Polyimide based resin composition

ABSTRACT

A molding resin composition comprising 99.9 to 50% by weight of polyimide represented by the formula: ##STR1## and 0.1 to 50% by weight of polyether ketone resin and/or polyester resin, and more particularly comprising the polyester resin capable of forming an anisotropical molten phase at a temperature of 420° C. or less, and a polyimide-based molding resin composition which comprises the said resins and other additives such as phenolic resin, fluororesin, graphite, carbon fibers, aromatic polyamide fibers, potassium titanate fibers and a crystallization accelerator, and is excellent in thermal resistance, chemical resistance, mechanical strength and processability.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 07/883,267, filed May 14, 1992 now U.S. Pat. No. 5,312,866, which is a continuation-in-part of application Ser. No. 07/617,147, filed on Nov. 23, 1990, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a molding resin composition which comprises polyimide resin as a principal component. More particularly, the invention relates to a polyimide-based molding resin composition which comprises polyimide resin and polyether ketone resin and/or polyester resin, and relates to a polyimide-based molding resin composition which comprises the said resins and other additives such as phenolic resin, fluororesin, graphite, carbon fiber, aromatic polyamide fiber, potassium titanate fiber and a crystallization accelerator, and is excellent in thermal resistance, chemical resistance, mechanical strength and processability.

2. Description of the Related Art

Conventionally, polyimide has outstanding thermal resistance, is excellent in mechanical strength and dimensional stability, and additionally has flame retardance and electrical insulation properties. Polyimide has hence been used in areas such as electrical and electronic parts, space and aeronautic members, and transportation equipment. In the future, it is expected that the use of polyimide will be extended to areas where thermal resistance is required. Various kinds of polyimide which exhibit excellent properties have been developed.

Although polyimide is excellent in thermal resistance, means such as sinter molding is generally required in the case of using polyimide as a molding material. Even though polyimide is thermoplastic and melt-moldable, processing under high temperature and high pressure is required in many cases. When polyimide is processed under such high temperature and pressure, polyimide is, though excellent in thermal resistance, thermally deteriorated or oxidized which decreases mechanical strength and which makes molding of thin-walled articles difficult.

Some kinds of polyimide have slow rates of crystallization in the processing stage and molded articles can be obtained in an amorphous state. Even though heat treatment is carried out in order to enhance the crystallinity of such polyimides, dimensional changes resulting from crystallization have led to severe restrictions on the application of such polyimides to areas such as precision parts.

On the other hand, when processability is improved, the polyimide has a lower glass transition temperature and is soluble in halogenated hydrocarbons. That is, the polyimide has decreased performance in view of thermal and solvent resistances. Consequently, conventionally proposed polyimides have both merits and drawbacks, and, it has been desired to accomplish further improvement.

The present inventors have also found a novel polyimide resin having recurring units represented by the formula (I): ##STR2## wherein X is a direct bond, divalent hydrocarbon having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl; Y₁, Y₂, Y₃ and Y₄ are individually hydrogen, lower alkyl, lower alkoxy, chlorine or bromine; R is a tetravalent radical selected from an aliphatic radical having 2 or more carbon atoms, alicyclic, monocyclic aromatic or fused polycyclic aromatic radical or a polycyclic aromatic radical connected to each other through a direct bond or a bridge member [Japanese Laid-Open Patent SHO 61-143478(1986), 62-68817(1987), 62-86021(1987), 62-235381(1987) and 63-128025(1988)].

The polyimide resin thus found is a novel thermal-resistant resin having various favorable properties such as excellent mechanical strength, thermal property, electrical property and solvent resistance in addition to its essential thermal resistance.

The polyimide resin is excellent in thermal resistance, mechanical strength and electrical properties as compared with conventional engineering plastics represented by polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polysulfone and polyphenylene sulfide. Consequently, the polyimide resin having improved processability in addition to its substantially outstanding characteristics can be expected to be used in fields where conventional engineering plastics are not satisfactory.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a polyimide-based molding resin composition having excellent flowability in a molten state in addition to its substantially outstanding characteristics.

Another object of the present invention is to provide a polyimide-based resin composition having an increased rate of crystallization and an improved dimensional stability of molded articles in a heat-treatment step.

Still another object of the invention is to provide a polyimide-based resin composition for low friction materials which has excellent sliding property and mechanical characteristics in addition to outstanding heat resistance and toughness.

A further object of the invention is to provide a polyimide-based resin composition for low friction materials which is excellent in sliding property, has improved processability without impairing the thermal properties of polyimide resin, and can be heat-treated for post-crystallization.

A still further object of the invention is to provide a polyimide-based resin composition which is excellent in heat resistance, dimensional stability of molded articles in the heat treatment step for post-crystallization and mechanical properties, and a polyimide-based resin composition having excellent mechanical characteristics and good dimensional stability in molding shrinkage.

An additional object of the invention is to provide a polyimide-based resin composition which is excellent in processability and has improved mechanical characteristics, heat resistance and chemical resistance due to an increased rate of crystallization.

As a result of an intensive investigation in order to accomplish these objects, the present inventors have found that a polyimide-based composition comprising the novel polyimide and polyether ketone resin and/or polyester resin is particularly effective for achieving the above objects.

They have further found a polyimide resin composition comprising polyimide resin and a thermotropic liquid crystal polymer wherein:

1 the sliding property can be remarkably improved by formulating a cured phenolic resin and a solid lubricant,

2 by formulating one or more additives selected from the group consisting of fluororesin, graphite and aromatic polyamide resin, the sliding property can be remarkably improved and the dimensional stability of molded articles in the heat treatment for post-crystallization is markedly enhanced to make heat treatment possible,

3 a high-strength sliding material having excellent sliding property and mechanical characteristics can be obtained by formulating a fluororesin and carbon fibers,

4 mechanical properties can be remarkably improved by formulating carbon fibers and wherein mechanical strength can be critically enhanced depending upon the amount of formulation,

5 a resin composition having remarkably improved mechanical properties and good dimensional stability of molded articles can be obtained by formulating potassium titanate fibers, and

6 the processability and crystallization rate of polyimide-based resin can be improved by adding a crystallization accelerator. Thus the present invention has been completed.

Accordingly, one aspect of the present invention is a resin composition comprising from 99.9 to 50% by weight of a polyimide having recurring units represented by the formula (I): ##STR3## wherein X, Y₁, Y₂, Y₃, Y₄ and R are the same as above, preferably represented by the formula (II): ##STR4## wherein X and R are the same as above, and from 0.1 to 50% by weight of a polyether ketone resin and/or a polyester resin.

In the resin composition of the present invention, the polyether ketone resin is preferably represented by the formula (III): ##STR5##

Further, in the resin composition of the present invention, the polyester resin has preferably recurring structural units represented by the formula (IV): ##STR6## wherein Y is an aliphatic radical having from 1 to 4 carbon atoms or a radical represented by ##STR7## wherein Z is a direct bond, ##STR8## the polyester resin can more preferably form an anisotropic molten phase at a temperature of 420° C. or less; and the polyester resin is most preferably a thermotropic liquid-crystal polymer obtained by conducting polymerization so that the polyester bond is formed by basic structural units of the formulas (V), (VI), (VII) and (VIII): ##STR9##

A second aspect of the invention is a polyimide resin composition for low friction materials comprising from 3 to 50 parts by weight of a cured phenolic resin and from 1 to 25 parts by weight of solid lubricant for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (I) and from 50 to parts by weight of a thermotropic liquid crystal polymer.

A third aspect of the invention is a polyimide resin composition for low friction materials comprising from 1 to 150 parts by weight of one or more additives selected from the group consisting of fluororesin, graphite and aromatic polyamide resin for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (I) and from 50 to 1 parts by weight of a thermotropic liquid crystal polymer.

A fourth aspect of the invention is a polyimide resin composition for low friction materials comprising from 1 to 60 parts by weight of fluororesin and from 5 to 160 parts by weight of carbon fibers for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (I) and from 50 to 1 parts by weight of a thermotropic liquid crystal polymer.

A fifth aspect of the invention is a carbon fiber reinforced polyimide resin composition comprising from 5 to 50 parts by weight of carbon fibers for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (I) and from 50 to 1 parts by weight of a thermotropic liquid crystal polymer.

A sixth aspect of the invention is a polyimide-based resin composition comprising from 5 to 200 parts by weight of potassium titanate fibers for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (]) and from 50 to 1 parts by weight of a thermotropic liquid crystal polymer.

A seventh aspect of the invention is a polyimide-based resin composition comprising from 0.01 to 25 parts by weight of a crystallization accelerator for 100 parts by weight of a resin composition comprising from 50 to 99 parts by weight of the polyimide having recurring units represented by the above formula (I) and from 50 to 1 parts by weight of a thermotropic liquid crystal polymer.

In these polyimide-based resin compositions which contain additional additives, the thermotropic liquid crystal polymer which can be preferably used is one or more polymers having basic structure selected from the group consisting of the above formulas (V), (VI), (VII) and VIII).

The fluororesin which can be preferably used in the third and fourth aspects of the invention is one or more fluororesins selected from the group consisting of the following (a) to (f).

(a) Tetrafluoroethylene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--.

(b) Tetrafluoroethylene-hexafluoropropylene copolymer resin having in the molecule recurring structural units represented by the formulas:

    --(CF.sub.2 CF.sub.2)--

    and

    --[CF(CF.sub.3)CF.sub.2 ]--.

(c) Tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin having in the molecule recurring structural units represented by the formulas:

    --(CF.sub.2 CF.sub.2)-- and

    --[CF(OC.sub.m F.sub.2m+1)CF.sub.2 ]--

wherein m is an integer.

(d) Tetrafluoroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--

    and

    --(CH.sub.2 CH.sub.2)--.

(e) Trifluorochloroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CFClCF.sub.2)-- and

    --(CH.sub.2 CH.sub.2)--.

(f) Fluorovinylidene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CH.sub.2)--.

The aromatic polyamide resin which can be used in the third aspect of the invention is preferably one or more resins selected from the group consisting of the formulas (IX), (X) and (XI): ##STR10##

Further, the preferred crystallization accelerator which can be used in the seventh aspect of the invention is one or more inorganic compounds selected from the group consisting of calcium chloride, aluminum phosphate, hydrotalcite compounds, sodium chloride and graphite, or one or more organic compounds represented by the formulas (XII) and (XIII): ##STR11## wherein R₁ is a tetravalent radical selected from the group consisting of an aliphatic radical and alicylic radical having from 2 to 10 carbon atoms, respectively, and phenyl radical, and may be the same as or different from R in the formula (I); and X₁ and X₂ are one or more radicals selected from the group consisting of hydrogen, chlorine, bromine, fluorine, lower alkyl and lower alkoxy radical having from 1 to 10 carbon atoms, respectively; and ##STR12## wherein K is an integer of from 1 to 10, X₃ is one or more divalent radicals selected from the group consisting of a direct bond, hydrocarbon having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio and sulfonyl; Y₅, Y₆, Y₇ and Y₈ are individually one or more divalent radicals selected from the group consisting of hydrogen, chlorine, bromine, lower alkyl and lower alkoxy radical having from 1 to 10 carbon atoms, respectively; R₂ is a tetravalent radical selected from the group consisting of an aliphatic radical and alicylic radical having from 2 to 10 carbon atoms, respectively, and phenyl; X₃, Y₅, Y₆, Y₇, Y₈ , and R may be individually the same as or different from the radicals having the same symbols in the formula (I); and Y, and Y₁₀ are --H, --NH₂ or ##STR13##

In any composition of the invention, the polyimide resin used preferably has an inherent viscosity of from 0.3 to 0.7 dl/g at 35° C. in a solution containing 0.5 g of the resin in 100 ml of a solvent mixture composed of 90 parts by weight of p-chlorophenol and 10 parts by weight of phenol.

The resin composition of the present invention has remarkably improved processability and enhanced dimensional stability of molded articles upon a heat treatment (annealing) step without impairing the excellent characteristics of the polyimide resin.

By blending a polyester capable of forming an anisotropic molten phase, the rate of crystallization is remarkably accelerated and the polyimide resin based composition can shift its exothermic temperature (Tc₁) of crystallization to the lower temperature side in a temperature-rise step.

The polyimide-based resin composition of the invention for low friction materials has excellent processability and the molded articles obtained from the composition have a low friction coefficient without impairing heat resistance and mechanical characteristics which are essential features of the above resin composition and is also extremely outstanding in wear resistance. The molded articles of the resin composition also have excellent dimensional stability in heat treatment. Further, the composition comprising the crystallization accelerator has a remarkably increased rate of crystallization in addition to the excellent processability and can provide in economy a resin having excellent mechanical characteristics and heat and chemical resistances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polyimide used in the present invention is represented by the above formula (I).

The polyimide can be prepared by reacting an ether diamine represented by the formula (XIV): ##STR14## wherein x, Y₁, Y₂, Y₃ and Y₄ are the same as above, preferably an ether diamine represented by the formula (XV): ##STR15## wherein X is the same as above, with one or more tetracarboxylic dianhydrides.

That is, the polyimide can be prepared by reacting the ether diamine with the tetracarboxylic dianhydride in a solvent and then thermally or chemically imidizing the resultant polyamic acid.

The reaction temperature is usually 250° C. or less. No particular restriction is imposed upon the reaction pressure. The reaction can be satisfactorily carried out under atmospheric pressure.

The reaction time varies depending upon the tetracarboxylic dianhydride used, the kind of solvent, and the reaction temperature.

The reaction is usually carried out for a time sufficient to complete formation of the polyamic acid intermediate. Sufficient reaction times are 24 hours or less, an hour or less in some cases.

The above reaction provides the polyamic acid corresponding to the recurring structural units of the formula (I). The polyamic acid is successively heat-dehydrated at 100° to 400° C. or chemically imidized by using a conventional imidizing agent to obtain the polyimide having recurring structural units of the formula (I).

Polyimide can also be prepared by simultaneously conducting polyamic acid formation and the heat-imidizing reaction.

The diamine compound for use in the preparation of the above polyimide which is used for the principal component in the composition of the present invention is represented by the above formula (XIV).

Exemplary diamine compounds include, for example:

bis[4-(3-aminophenoxy)phenyl]methane,

1,1-bis[4-(3-aminophenoxy)phenyl]ethane,

1,2-bis[4-(3-aminophenoxy)phenyl]ethane,

2,2-bis[4-(3-aminophenoxy)phenyl]propane,

2-[4-(3-aminophenoxy)phenyl]-2-(4-(3-aminophenoxy)-3-methylphenyl] propane,

2,2-bis[4-(3-aminophenoxy)-3-methylphenyl]propane,

2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane,

2,2-bis[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane,

2,2-bis[4-(3-aminophenoxy)phenyl]butane,

2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,

4,4'-bis(3-aminophenoxy)biphenyl,

4,4'-bis(3-aminophenoxy)-3-methylbiphenyl,

4,4'-bis(3-aminophenoxy)-3,3'-dimethylbiphenyl,

4,4'-bis(3-aminophenoxy)-3,5-dimethylbiphenyl,

4,4'-bis(3-aminophenoxy)-3,3',5,5'-tetramethylbiphenyl,

4,4'-bis(3-aminophenoxy)-3,3'-dichlorobiphenyl,

4,4'-bis(3-aminophenoxy)-3,5-dichlorobiphenyl,

4,4'-bis(3-aminophenoxy)-3,3',5,5'-tetrachlorobiphenyl,

4,4'-bis(3-aminophenoxy)-3,3'-dibromobiphenyl,

4,4'-bis(3-aminophenoxy)-3,5-dibromobiphenyl,

4,4'-bis(3-aminophenoxy)3,3',5,5'-tetrabromobiphenyl,

bis[4-(3-aminophenoxy)phenyl]ketone,

bis[4-(3-aminophenoxy)phenyl]sulfide,

bis[4-(3-aminophenoxy)-3-methoxyphenyl]sulfide,

[4-(3-aminophenoxy)phenyl][4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide,

bis[4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide,

bis[4-(3-aminophenoxy)phenyl]sulfone,

bis[4-(3-aminophenoxy)phenyl]ether,

bis[4-(4-aminophenoxy)phenyl]ether,

1,4-bis[4-(3-aminophenoxy)phenoxy]benzene,

1,4-bis[4-(4-aminophenoxy)phenoxy]benzene,

1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,

1,3-bis[4-(3-aminophenoxy)benzoyl]benzene,

bis[4{4-(4-aminophenoxy)phenoxy}phenyl]sulfone,

and bis[4{4-(4-aminophenoxy)phenoxy}phenyl]ketone.

The diamine compound may be used a single compound or a mixture thereof.

The tetracarboxylic dianhydride which is another raw material for preparing polyimide of the formula (I) is represented by the formula (XVI): ##STR16## wherein R is the same as above.

In the tetracarboxylic dianhydride represented by the formula (XVI), R is preferably a tetravalent radical represented by the formula (XVII): ##STR17## wherein X₄ is a direct bond, --O--, --S--, --SO₂, --CH₂, --CO--, --C(CH₃)₂ --, --C(CF₃)₂ -- R1 ? ##STR18## wherein Y₁₁ is a direct bond, --O--, --S--, --SO₂ --, --CH₂ --, --CO--, --C(CH₃)₂ -- or --C(CF₃)₂ --.

Consequently, in the polyimide of the formula (I), R is preferably represented by the formula (XVII).

The tetracarboxylic dianhydrides used as a raw material in the preparation of polyimide include, for example,

ethylenetetracarboxylic dianhydride,

butanetetracarboxylic dianhydride,

cyclopentanetetracarboxylic dianhydride,

pyromellitic dianhydride,

3,3',4,4'-benzophenonetetracarboxylic dianhydride,

2,2',3,3'-benzophenonetetracarboxylic dianhydride,

3,3',4,4'-biphenyltetracarboxylic dianhydride,

2,2',3,3'-biphenyltetracarboxylic dianhydride,

2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,

2,2-bis(2,3-dicarboxyphenyl)propane dianhydride,

bis[3,4-dicarboxyphenyl)ether dianhydride,

bis(3,4-dicarboxyphenyl)sulfone, dianhydride,

1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride,

bis(2,3-dicarboxyphenyl)methane dianhydride,

bis(3,4-dicarboxyphenyl)methane dianhydride,

-[4-(3,4-dicarboxyphenoxy)phenoxy]phthalic dianhydride,

2,3,6,7-naphthalenetetracarboxylic dianhydride,

1,4,5,8-naphthalenetetracarboxylic dianhydride,

1,2,5,6-naphthalenetetracarboxylic dianhydride,

1,2,3,4-benzenetetracarboxylic dianhydride,

3,4,9,10-perylenetetracarboxylic dianhydride,

2,3,6,7-anthracenetetracarboxylic dianhydride,

and 1,2,7,8-phenanthrenetetracarboxylic dianhydride.

The tetracarboxylic dianhydride can be used singly or in combination.

The polyimide used in the composition of the invention is prepared by using the above ether diamine as a raw material. The polyimide prepared by simultaneous use of other diamines can also be used for the composition of the invention as long as no adverse effect is found on the good properties of the polyimide.

Exemplary diamines which can be simultaneously used include m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, bis(3-aminophenyl) ether, (3-aminophenyl)(4-aminophenyl) ether, bis(4-aminophenyl) ether, bis(3-aminophenyl) sulfide, (3-aminophenyl)(4-aminophenyl) sulfide, bis(4-aminophenyl) sulfide, bis(3-aminophenyl) sulfoxide, (3-aminophenyl)(4-aminophenyl) sulfoxide, bis(4-aminophenyl) sulfoxide, bis(3-aminophenyl) sulfone, (3-aminophenyl)(4-aminophenyl) sulfone, bis(4-aminophenyl) sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,4-bis[4-(4-aminophenoxy)benzyl]benzene, and 1,4-bis[4-(4-aminophenoxy)benzyl]benzene.

The resin composition of the present invention can be obtained by blending the above polyimide resin with the following components.

That is, the component to be blended with the polyimide resin in the composition of the invention is polyether ketone resin, polyester resin or a mixture of these resins.

Polyether ketone resin is a thermoplastic resin having recurring units represented by the above formula (III): ##STR19## For example, a representative commercial product is VICTREX PEK (Trade Mark of I.C.I. Ltd.).

Polyester resin used in the invention includes the following types of resins.

1 A polymer obtained by the reaction of at least one divalent phenol, aliphatic diol and/or alicyclic diol with at least one dicarboxylic acid and/or a dicarboxylic acid derivative.

2 A copolymer consisting of at least three components and having a polyester structure as a whole, the copolymer comprising at least one divalent phenol, aliphatic diol and/or alicyclic diol; at least one dicarboxylic acid and/or a dicarboxylic acid derivative; and additionally at least one hydroxycarboxylic and/or a hydroxycarboxylic acid derivative.

The copolymer may contain polyester obtained by reacting at least one hydroxycarboxylic acid and/or its derivative.

Exemplary polyesters include those illustrated below.

1) The polyester resin consisting principally of one or two component polyesters obtained by the reaction of a divalent phenol, aliphatic diol or alicyclic diol with a dicarboxylic acid or dicarboxylic acid derivative, or with a hydroxycarboxylic acid or hydroxycarboxylic acid derivative, and having recurring units represented by the following formulas: ##STR20## wherein two carbonyl radicals are situated with respect to each other in the ortho, meta or para position or mixture of these positions in the formulas from 3 to ○ 10 and X is hydrogen, fluorine, chlorine, bromine or an alkyl radical in the formula ○ 10 .

2) The copolymer consisting of at least three components, a having polyester structure as a whole, and having a combination of a divalent phenol or diol radical, dicarboxylic acid radical and a hydroxycarboxylic acid radical, the combination being illustrated by the formulas: ##STR21##

The polyester used for the invention is of course not limited to those illustrated above.

Many kinds of polyesters having various polymerization degrees are commercially available and the polyester having a suitable melt viscosity characteristic for the desired composition can be arbitrarily selected in the market.

The polyester resin has preferably recurring structural units represented by the formula (IV): ##STR22## wherein Y is an aliphatic radical having from 1 to 4 carbon atoms or a radical represented by ##STR23## wherein Z is a direct bond, --C(CH₃)₂ --, --SO₂ --, --CH₂ --, --O--, --CO-- or ##STR24## ; the polyester resin can more preferably form an anisotropic molten phase; and the most preferred polyester resin forms the molten phase at a temperature of 420° C. or less.

The polyester which forms such anisotropic molten phase, that is, the polyester which is a so-called thermotropic liquid-crystal polymer is most preferably obtained by carrying out polymerization so that polyester bond is formed by basic structural units of the formulas (V), (VI) ,(VII) and (VIII): ##STR25##

The molding resin composition of the invention is prepared by blending from 99.9 to 50% by weight of the above polyimide resin and from 0.1 to 50% by weight of the polyether ketone resin and/or the polyester resin.

The resin composition of the invention exhibits remarkable low melt viscosity in a high temperature range of 300° C. or more. The polyester resin provides a good fluidizing effect on the resin composition and the effect can be observed even in a small amount. The lower limit of the polyester resin content in the composition is 0.1%, preferably 0.5% by weight.

The composition obtained by using a polyester which does not form an anisotropic molten phase is insufficient in chemical resistance and mechanical strength as compared with the composition obtained by using polyester which forms an anisotropic molten phase. On the other hand, the polyester which forms an anisotropic molten phase can provide excellent performance, that is, chemical resistance, flame retardance and mechanical strength which are superior to those of conventional thermal-resistant resins.

When some kinds of anisotropic molten phase forming polyesters are used in a large amount, it is liable to cause problems such as too high anisotropy of mechanical properties, formation of fibrils, and insufficient weld strength. Thus the polyester resin is controlled to a smaller amount in the composition. Usually the preferred amount of the polyester resin is 50% by weight or less.

The composition of the invention can be prepared by generally known processes. For example, preferred processes are illustrated below.

1 A process for preparing powder by preblending polyimide resin powder and polyester ketone resin powder and/or polyester resin powder in a mortar, Henschel mixer, drum blender, tumbler, ball mill and ribbon blender.

2 A process for preparing powder by previously dissolving or suspending polyimide resin powder in an organic solvent, adding polyether ketone resin and/or polyester resin to the resulting solution or suspension, dispersing uniformly and thereafter removing the solvent.

3 A process for preparing powder by suspending polyether ketone resin and/or polyester resin in an organic solvent solution of polyamic acid which is the precursor of polyimide in the invention, carrying out heat-treatment at 100° to 400° C. or chemical imidization by using a conventional imidizing agent, and then removing the solvent.

The powdery polyimide resin composition thus obtained can be used as such for various molding processes, for example, injection molding, compression molding transfer molding. However, molding is more preferably carried out after melting and mixing each component of the composition.

In the preparation of a melt-mixed composition, it is also a simple and effective method to mix and mold powders with each other, pellets with each other, or powder and pellets.

Melt-mixing can be conducted by utilizing equipment for melt-blending common rubber or plastics, for example, hot rolls, Banbury mixer, Brabander and an extruder.

Melt-mixing is carried out in the range of from the melt temperature to the decomposition-initiating temperature of the formulation. The temperature is usually from 250° to 420° C., preferably from 300° to 400° C.

As to the process for molding the resin composition of the invention, a suitable process is injection molding or extruding which is a process capable of forming a uniformly melted blend and which has a high productivity. Other molding processes such as transfer molding, compression molding and sinter molding can also be applied without any problem.

In the present invention, one or more additives can be added to the composition, if desired.

Exemplary additives which can be used include, fillers such as calcium carbonate, mica, glass beads, graphite, and molybdenum disulfide; fiber reinforcements such as glass fibers, carbon fibers, ceramic fibers, aramide fibers, potassium titanate fibers and metal fibers; lubricants; release agents; stabilizers; colorants; other thermoplastic resin such as polyphenylene sulfide, polyether imide, polyether sulfone, and polyether ether ketone; and thermosetting resins such as phenol resin, epoxy resin, silicone resin and polyamide imide resin.

1 The composition of the invention comprising these other additives will be illustrated hereinafter.

The various compositions described below are polyimide-based compositions obtained by adding other additives to the polyimide composition comprising 50 to 99% by weight of polyimide resin represented by the formulas (I) and (II) and from 50 to 1% by weight of a thermotropic liquid crystal polymer which are fundamental components.

In these resin compositions, the proportion of the thermotropic liquid crystal polymer exceeding 50% by weight decreases weld strength of the resultant resin composition and anisotropy becomes dominant. A proportion less than 1% by weight leads to insufficient processability and slow rate of crystallization in the resulting resin composition and dimensional stability of molded articles in the heat-treatment (annealing) step cannot be improved.

Particularly preferred polyimide used in these resin compositions has the above formula (I) wherein R is an aliphatic radical having from 4 to 9 carbon atoms, alicyclic radical having from 4 to 10 carbon atoms, monoaromatic radical having the formula: ##STR26## condensed polyaromatic radical having the formula: ##STR27## , and noncondensed aromatic radical which is obtained by connecting aromatic radicals each other with a direct bond or a bridge member and has the formula: ##STR28## wherein X₄ is a direct bond, --O--, --S--, --SO₂, --CH₂, --CO--, --C(CH₃)₂ --, ##STR29## wherein Y₁₁ is a direct bond, --O--, --S--, --SO₂ --, --CH₂ --, --CO--, --C(CH₃)₂ -- or --C(CF₃)₂ --.

The polyimide resin has an inherent viscosity of usually in the range of from 0.35 to 0.65 dl/g, preferably from 0.40 to 0.60 dl/g. The inherent viscosity is measured at 35° C. in a solution containing 0.5 g of the polyimide in 100 ml of a solvent mixture consisting of 90% by weight of p-chlorophenol and 10% by weight of phenol. When the inherent viscosity is less than 0.35 dr/g, mechanical properties and durability are unsatisfactory. On the other hand, an inherent viscosity exceeding 0.65 dl/g impaired processability and injection molding becomes difficult.

A composition which comprises other additives of the invention is a polyimide-based resin composition for low friction materials (hereinafter referred to as composition B) which comprises cured. phenolic resin and solid lubricant in addition to the polyimide represented by the above formula (II) and the thermotropic liquid crystal polymer.

In the composition B, a preferred polyimide is represented by the formula(II) and a preferred thermotropic liquid crystal polymer has the formulas (V), (VI), (VII) and (VIII).

Cured phenolic resin is prepared by reacting phenols with a formaldehyde generating compound, adding conventionally known fillers to the resulting novolak type or resol type resin, if desired, heating the thus-obtained mixture as intact or after adding a crosslinking agent such as hexamethylenetetramine and crushing the resultant cured product. The preparation process has been disclosed in Japanese Laid-Open Patents Sho 57-17701 and 58-17114 and many other patents. Marketed products include Bellpearl (Trade mark; Kanebo Co.).

The cured phenolic resin which can be used for the composition of the invention is a heat infusible resin in the form of granules or powder. The phenolic resin has an average particle size of 50 μm or less and 80% by weight or more of the resin preferably has a particle size of 150 μm or less.

In the case of too large a particle size of the cured phenolic resin, adhesion of particles to each other in the powder becomes insufficient in the molding step, leads to fluctuation in the properties of the molded articles and unfavorably lowers mechanical strengths such as wear resistance and flexural strength.

The phenol resin must be cured sufficiently. The degree of cure is indicated, for example, by "methanol solubility as a scale. Methanol Solubility is measured by accurately weighing about 10 g of the resin sample (the weight is W₀), heat-treating the sample under reflux of 500 ml of 100% methanol for 30 minutes, followed by filtering through a glass filter, washing the filter residue with 100 ml of methanol and drying the residue at 70° C. for 2 hours (the dried weight of the residue is W₁). The methanol solubility is calculated by the following equation. ##EQU1##

The methanol solubility of the cured phenolic resin is usually 20% by weight or less, preferably 15% by weight or less. When the methanol solubility exceeds 20% by weight, vaporization takes place in the molding step and the molded article unfavorably generates voids or fine cracks in some cases.

The amount of the cured phenolic resin is in the range of from 3 to 50 parts by weight, preferably from 8 to 40 parts by weight for 100 parts by weight of the sum of the polyimide resin and the thermotropic liquid crystal polymer. An amount less than 3% by weight is not effective for wear resistance. On the other hand, amount exceeding 50% by weight leads to an increase melt viscosity of the composition which makes melt molding impossible and additionally the friction coefficient cannot be lowered, which is unfavorable for sliding materials.

The solid lubricant for use in the composition of the invention is blended together with the above cured phenolic resin in order to improve the sliding property of the matrix resin. Exemplary solid lubricants include tetrafluoroethylene resin (hereinafter referred to as PTFE), graphite, molybdenum disulfide, wolfram disulfide, fluorographite, boron nitride, silicon nitride and metal oxides such as lead monoxide.

The amount of the solid lubricant is usually from 1 to.25 parts by weight, preferably from 3 to 14 parts by weight for 100 parts by weight of the sum of the polyimide resin and the thermotropic liquid crystal polymers. When the amount is less than 1 parts by weight no improvement is found on the sliding property. On the other hand, an amount exceeding 25 parts by weight lowers essential mechanical strength of the aromatic polyimide resin.

The polyimide-based resin composition of the invention for low friction materials can be further blended, if desired, with other materials including carbon fibers, glass fibers, optical fibers, ceramic fibers, potassium titanate fibers, metal fibers, boron fibers, silicon carbide fibers, asbestos, rock wool and other fibrous reinforcement; calcium carbonate, mica, glass beads, graphite, molybdenum disulfide, clay, silica, alumina, talc, diatomaceous earth, hydrated alumina, silicate balloons and other fillers; lubricants, releasing agents, stabilizers, colorants, crystal nucleating agents and other miscellaneous additives; other thermoplastic resins such as polyphenylene sulfide, polyetherimide, polyether sulfone and polyether ketone; and thermosetting resins such as epoxy resin, silicone resin and polyamideimide resin.

No particular restriction is imposed on the means for mixing various raw materials in order to prepare the polyimide-based resin composition of the invention for sliding materials. The raw materials can be individually fed to a melt kneader. Alternatively, the raw materials can be previously mixed with a common mixer such as Henschel mixer, ball mixer and ribbon blender and then fed to the melt kneader. Melt kneading is usually carried out at 250° to 420° C. , preferably 300° to 400° C.

The polyimide-based resin composition of the invention for sliding materials can of course be hot-molded by compression molding or sinter molding, or can be processed by injection molding or extrusion forming with high productivity after forming uniform molten blend.

Other compositions are polyimide-based resin compositions for low friction materials (hereinafter referred to as composition C) which comprises one or more components selected from the group consisting of fluororesin, graphite and aromatic polyamide resin in addition to the polyimide represented by the above formula (I) and the thermotropic liquid crystal polymer.

The term fluororesin means a synthetic high polymer containing fluorine atoms (F) in the molecule. The fluororesin is generally excellent in heat resistance, chemical resistance and electrical characteristics as compared with other synthetic resins and also has essentially low friction features and nonadhesive property.

Practical examples are one or more fluororesins selected from the group consisting of the following (a) to (f).

(a) Tetrafluoroethylene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2),

(b) Tetrafluoroethylene-hexafluoropropylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--

    and

    --[CF(CF.sub.3)CF.sub.2 ]--.

(c) Tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin having in the molecule recurring structural units represented by the formulas:

    --(CF.sub.2 CF.sub.2)--

    and

    --(CF(OC.sub.m F.sub.2+1)CF.sub.2 ]--

wherein m is an integer.

(d) Tetrafluoroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--

    and

    --(CH.sub.2 CH.sub.2)--.

(e) Trifluorochloroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CFClCF.sub.2)--

    and

    --(CH.sub.2 CH.sub.2)--.

(f) Fluorovinylidene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CH.sub.2)--.

Particularly, tetrafluoroethylene resin (PTFE) of the formula (a) is outstanding in these properties and is most preferably used in the composition C.

The fluororesin used in the Polyimide-based resin composition C is usually in the form of powder and has a particle size of from 1 to 5 μm, preferably from 5 to 10 μm.

The aromatic polyamide resin which can be used in the third aspect of the invention is preferably one or more resins having recurring units selected from the group consisting of the formulas (IX), (X) and (XI): ##STR30##

The aromatic polyamide resin is a heat resistant resin which has been marketed recently and is expected to develop in various fields by utilizing its specific properties. Representative examples of the aromatic polyamide resin include those having the above structural unit (IX), (X) and (XI), that is, the aromatic polyamide resin having one or more of the above recurring structural units in any molecule or a mixture of two or more aromatic polyamide resin having these structural units.

The aromatic polyamide resins which can be used in the invention are marketed, for example, in the name of "Kevlar" (Trade mark; E. I. Du Pont de Nemours & Co.), "Nomex" (Trade mark; E. I. Du Pont de Nemours & Co.), "Conex" (Trade mark; Teijin) and "Technole" (Trade mark; Teijin).

Other aromatic polyamide resins having various kinds of skeletons are provided according to ortho-, meta- and para-isomer structure. The resin having para-para bonding of the formula (IV) has an extremely high softening point and melting point and can be most preferably used as a heat resistant resin in the invention.

The fluororesin, graphite and the aromatic polyamide resin are added in a total amount of these additives of from 1 to 150 parts by weight for 100 parts by weight of the above resin composition comprising the polyimide resin and the thermotropic liquid crystal polymer.

When the total amount of these additives is less than 1 part by weight, the effect for improving wear resistance is small. On the other hand, a total amount exceeding 150 parts by weight is unfavorable because processability and mechanical characteristics of resulting resin composition are impaired and dimensional change of molded articles is increased in the heat treatment for post-crystallization.

Similar to the above composition B, other ingredients can be added to the composition of the invention, if desired, to prepare a composition in a similar manner.

Another composition is a polyimide-based resin composition for low friction materials (hereinafter referred to as composition D) comprising fluororesin and carbon fibers in addition to the polyimide resin represented by the above formula (II) and the thermotropic liquid polymer.

In the composition D, the proportion of the polyimide resin to the thermotropic liquid polymer is the same as above.

The fluororesin that can be used in the composition D is the same as above. Practical examples are one or more fluororesins selected from the group consisting of the above described (a) to (f).

Particularly, tetrafluoroethylene resin (PTFE) of the formula (a) is outstanding in these properties and is most preferably used in the composition D.

The fluororesin used in the polyimide-based resin composition D is usually in the form of powder and has a particle size of from 1 to 25 μm, preferably from 5 to 10 μm.

The amount of the fluororesin is in the range of from 1 to 60 parts by weight for 100 parts by weight of the polyimide resin composition comprising the polyimide resin of the above formula (I) and the thermotropic liquid crystal polymer. An amount less than 1 part by weight leads to inferior abrasion resistance of the resulting resin composition. On the other hand, an amount exceeding 60 parts by weight leads to inferior mechanical strength of the resulting resin composition.

The amount of the carbon fibers is in the range of from 5 to 100 parts by weight for 100 parts by weight of the polyimide resin composition comprising the polyimide resin of the above formula (I) and the thermotropic liquid crystal polymer. An amount less than 5 parts by weight impairs mechanical characteristics of the resulting resin composition. On the other hand, an amount exceeding 100 parts by weight leads to inferior processability of the resulting resin composition.

Similar to the above composition B, other ingredients can be added to the composition of the invention, if desired, to prepare a composition in a similar manner.

Another composition is a carbon-fiber reinforced polyimide-based resin composition (hereinafter referred to as composition E) comprising carbon fibers in addition to the polyimide resin represented by the above formula (II) and the thermotropic liquid polymer.

In the composition E, the proportion of the polyimide resin to the thermotropic liquid polymer is the same as above. The thermotropic liquid polymer is in the range of preferably from 40 to 1% by weight, more preferably from 30 to 2% by weight of the polyimide resin.

The rate of crystallization is remarkably increased by mixing the thermotropic liquid polymer which can form a nematic liquid crystal phase. As a result, the crystallization temperature can be shifted to the low temperature side in a temperature increasing step and to the high temperature side in temperature decreasing step.

The amount of the carbon fibers is in the range of from 5 to 100 parts by weight for 100 parts by weight of the polyimide resin composition comprising the polyimide resin of the above formula (I) and the thermotropic liquid crystal polymer. An amount less than 5 parts by weight impairs the mechanical characteristics of the resulting resin composition. On the other hand, an amount exceeding 100 parts by weight leads to inferior processability of the resulting resin composition.

Similar to the above composition B, other ingredients can be added to the composition of the invention, if desired, to prepare a composition in a similar manner.

Still another composition is a potassium titanate fiber reinforced polyimide-based resin composition (hereinafter referred to as composition F) comprising potassium titanate fibers in addition to the polyimide resin represented by the above formula (I) and the thermotropic liquid crystal polymer.

The potassium titanate fibers which can be used in the invention are a kind of whisker and a needle-like crystals having a fundamental, chemical composition K₂ O.6TiO₂, K₂ O.6TiO₂.H₂ O. A representative melting point is from 1300° to 1350° C. An average fiber length is usually from 5 to 50 μm, preferably from 20 to 30 μm. An average fiber diameter is usually from 0.05 to 1.0 μm, preferably from 0.1 to 0.3 μm. The potassium titanate fiber can be usually appliance untreated. However, the fibers can also be pretreated with silane coupling agents such as aminosilane and epoxysilane or surface treating agents such as chromic chloride in order to increase compatibility with the matrix resin of the invention depending upon the object for use.

The amount of the potassium titanate fibers is in the range of from 5 to 200 parts by weight for 100 parts by weight of the above resin composition comprising the polyimide resin and the thermotropic liquid crystal polymer. Preferably, the amount of the potassium titanate fiber is in the range of from 5 to 100% by weight.

An amount of the potassium titanate fibers less than 5 parts by weight results in inferior mechanical properties of the resulting resin composition and not very good dimensional stability of the molded articles in the heat treatment. On the other hand, an amount of the fibers greater than 200 parts by weight leads to insufficient processability of the resulting resin composition.

Similar to the above composition B, other ingredients can be added to the composition E of the invention, if desired, to prepare a composition in a similar manner.

A further composition is a polyimide-based resin composition (hereinafter referred to as composition G) comprising a crystallization accelerator in addition to the polyimide resin represented by the above formula (I) and the thermotropic liquid crystal polymer.

The crystallization accelerator which is used as a required component in the composition G is an inorganic compound selected from the group consisting of calcium chloride, aluminum phosphate, hydrotalcite compounds, sodium chloride and graphite or an organic compound having the formula (XII) or (XIII).

In these accelerators, calcium chloride exists in the form of anhydrous salt, mono-, di-, tetra- and hexa-hydrate, and any of these compounds can be used for the invention.

Aluminum phosphate exists in the form of orthophosphates such as an anhydrous salt having the structure AlPO₄ and hydrated salt having the structure AlPO₄. 4H₂ O, AlPO₄.3.5H₂ O, and metaphosphates such as Al(PO₃)₃. Any of these phosphates can be used for the invention.

The term hydrotalcite compounds mean mineral hydrotalcite which is produced in Ural district, Russia and Snarum district, Norway and has a chemical structure Mg₆ Al₂ (OH)₁₆ CO₃.4H₂ O, and a synthetic product which has a similar structure Mg₄ 5 Al₂ (OH)₁₃ Co₃.5H₂ O or a product of Kyowa Kagaku Kogyo Co. having a structure Mg₄ 2 Al₂ (OH)₁₂ 4CO₃.5H₂ O. These compounds are usually applied in the form of powder.

Sodium chloride which can be used in the invention is a common product having purity of 95% or more.

Graphite is an allotropic form of carbon and is a natural product or an artificial product manufactured by heat treatment of pitch coke. Graphite is usually used as an auxiliary material of resins. Marketed graphite includes Lonza Graphite Powder (manufactured by Lonza Japan Co.) and can be used as a crystallization accelerator.

The organic crystallization accelerators which can be used for the composition of the invention include one or more imide oligomer represented by the formulas (XII) and (XIII): ##STR31## wherein R₁ is a tetravalent radical selected from the group consisting of an aliphatic radical and alicyclic radical having from 2 to 10 carbon atoms, respectively, and phenyl radical, and may be the same as or different from R in the formula (I); and X₁ and X₂ are one or more radicals selected from the group consisting of hydrogen, chlorine, bromine, fluorine, lower alkyl and lower alkoxy radical having from 1 to 10 carbon atoms, respectively; and ##STR32## wherein K is an integer of from 1 to 10, X₃ is one or more divalent radicals selected from the group consisting of a direct bond, hydrocarbon having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio and sulfonyl; Y₅, Y₆, Y₇ and Y₈ are individually one or more divalent radicals selected from the group consisting of hydrogen, chlorine, bromine, lower alkyl and lower alkoxy radical having from 1 to 10 carbon atoms, respectively; R₂ is a tetravalent radical selected from the group consisting of an aliphatic radical and alicylic radical having from 2 to 10 carbon atoms, respectively, and phenyl; X₃, Y₅, Y₆, Y₇, Y₈ and R may be individually the same as or different from the radicals having the same symbols in the formula (I); and Y₉ and Y₁₀ are --H, --NH₂ or ##STR33##

The above imide oligomers can be usually prepared by the addition of a chain stopper in the polycondensation of polyimide resin.

The imide oligomer having the formulas (XII) or (XIII) is obtained by blocking the molecular chain end with an organic mono diamine or a dicarboxylic acid anhydride such as phthalic anhydride.

A portion or the whole of these blocking agents can be replaced by other dicarboxylic acid anhydrides in the range not impairing the object of the invention.

Exemplary other dicarboxylic acid anhydrides which can be used in place of these blocking agents include

2,3-benzophenonedicarboxylic anhydride,

3,4-benzophenonedicarboxylic anhydride,

2,3-dicarboxyphenyl phenyl ether anhydride,

3,4-dicarboxyphenyl phenyl ether anhydride,

2,3-biphenyldicarboxylic anhydride,

3,4-biphenyldicarboxylic anhydride,

2,3-dicarboxyphenyl phenyl sulfone anhydride,

3,4-dicarboxyphenyl phenyl sulfone anhydride,

2,3-dicarboxyphenyl phenyl sulfide anhydride,

3,4-dicarboxyphenyl phenyl sulfide anhydride,

1,2-naphthalenedicarboxylic anhydride,

2,3-naphthalenedicarboxylic anhydride,

1,8-naphthalenedicarboxylic anhydride,

1,2-anthracenedicarboxylic anhydride,

2,3-anthracenedicarboxylic anhydride and

1,9-anthracenedicarboxylic anhydride.

The amount of the crystallization accelerator used in the invention is in the range of from 0.01 to 25 parts by weight, preferably from 0.05 to 10 parts by weight for 100 parts by weight of the resin composition comprising the polyimide resin and the thermotropic liquid crystal polymer. When the amount of the accelerator is less than 0.01 part by weight, almost no increase is observed in the rate of crystallization. On the other hand, an amount of the accelerator exceeding 25 parts by weight severely decreases the mechanical strength of the molded articles.

Similar to the above composition B, other ingredients can be added to the composition G of the invention, if desired, to prepare a composition in a similar manner.

The present invention will hereinafter be illustrated further in detail by way of examples and comparative examples.

In the examples and comparative examples, physical properties were determined by the following methods.

Inherent viscosity

0.5 g of polyimide powder was dissolved in 100 ml of a solvent mixture consisted of p-chlorophenol/phenol in a ratio of 9/1 by weight. Measurement was conducted after cooling the solution to 35° C.

Tensile strength

Measured in accordance with ASTM D-638 by using a tensile test specimen without a weld and a tensile test specimen welded at the center of the parallel portion.

Elongation at break

Measured in accordance with ASTM D-638.

Izod impact strength

Measured in accordance with ASTM D-258.

Heat distortion temperature (HDT)

Measured in accordance with ASTM D-648.

Melt Flow Ratio (MFR)

Measurements of Examples 8˜12 and Comparative Examples 5˜7 were conducted at 400° C., under 1.05 kg load in accordance with JIS K-7210, on the other hand MFRs of Examples 77˜96 and Comparative Examples 47˜52 were measured at 400° C., under 2.16 kg load in accordance with JIS K-7210.

Spiral flow length:

Measurement was conducted at a cylinder temperature of 400° C., mold temperature of 180° C., injection pressure of 1000 kg/cm² and cavity thickness of 1 mm.

Heat shrinkage

Heat treatment was carried out under the below described conditions on a tensile test specimen in accordance with ASTM D-638. Dimensional change in the longer direction of the specimen was measured before and after the heat treatment. Heat treatment carried out in three heating steps, 150° C.×20 hrs→260° C.×20 hrs→300° C.×2 hrs.

Warpage

Injection molded plate (75×100×2 mm) is heated and change of warpage height in longer direction was measured between before and after treatment.

Peak temperature (Tc) of crystallization exotherm

Peak temperature (Tc₁) of crystallization exotherm under a temperature-rise rate of 10° C./min from the room temperature and peak temperature (Tc₂) of crystallization exotherm under a temperature-fall rate of 10° C./min from 400° C. were measured by using a differential scanning calorimeter.

Coefficient of linear thermal expansion

Coefficient of linear thermal expansion from 25° to 200° C. was measured with a thermal expansion tester unwelded tensile specimens in the flow direction (MD) and the transverse direction (TD).

The ratio TD/MD of the linear expansion coefficient was assumed as being anisotropic

Dynamic friction coefficient (1)

In the case of Examples 22˜28 and Comparative Examples 18˜24 measured with a thrust type friction and wear tester at a face pressure of 1.1 kg/cm², sliding velocity of 150 m/min. and operating time of 60 minutes under a lubricant-free condition for a friction material of SUJ 2. On the other hand, in the case of Examples 29-45, 36˜76 and Comparative Examples 25˜32, 42˜46, measured with a thrust type friction and wear tester at a face pressure of 10 kg/cm², sliding velocity of 7 m/min. and operating time of 40 minutes under a lubricant-free condition for a friction material of stainless steel 45 C.

Wear coefficient

(1) Measured with the thrust type friction and wear tester at a face pressure of 0.78 kg/cm², sliding velocity of 128 m/min, and operating time of about 100 hours under a lubricant-free condition for a wear material of SUJ 2, in the case of Examples 22˜28 and Comparative Examples 18˜24.

(2) Measured with the cylindrical type friction and wear tester at the face pressure of 5 kg/cm², sliding velocity of 90 m/min, and operating time of about 40 hours under a lubricant-free condition for a wear material of stainless steel 45 C in the case of Examples 29˜45 and Comparative Examples 25˜32.

(3) Measured with the cylindrical type friction and wear tester at the face pressure of 5 kg/cm², sliding velocity of 100 m/min, and operating time of about 60 hours under a lubricant-free condition for a wear material of SUS 304, in the case of Examples 63476 and Comparative Examples 42˜46.

Softening temperature (°C.)

Measured by penetration initiating time in TMA penetration method with a thermo-mechanical analyzer TM-30 (Trade mark; Shimadzu Seisakusho Co.) at a temperature increase rate of 5° C./min and pressure of 18.6 kg/cm².

Limit of PV value

A limit of PV value of an untreated material was measured by using a thrust type wear tester at a sliding load of 40 kg/cm² under a lubricant-free condition for an friction material of SUS 304.

A specimen after heat treatment accompanied with crystallization in three heating steps, 150° C.×20 hrs→260° C.×20 hrs→300° C.×2 hrs, was also measured a limit of PV value under the same conditions as above.

Dimensional change due to heat treatment accompanied with crystallization

A plate which was injection molded under the above conditions and had dimensions of 75 mm×100 mm×1.5 mm^(t), was heat treated and dimensional change in the flow direction (hereinafter referred to as MD) and the transverse direction (hereinafter referred to as TD) was measured before and after the heat treatment. The heat treatment was carried out in three steps; 150° C.×20 hrs→260° C.×20 hrs→300° C.×2 hrs.

Molding shrinkage

A plate which was injection molded under the above conditions and had dimensions of 50 mm×50 mm×3 mm was used as a specimen for measuring molding shrinkage. A film gate having a thickness of 1 mm was fitted on an edge having a length of 50 mm. The melt-flow direction was indicated by MD (Machine Direction) and the rectangular direction was indicated by TD (Transverse Direction).

EXAMPLES 1-4

Polyimide powder having an inherent viscosity of 0.90 dl/g and a glass transition temperature of 235° C. was prepared from bis[4(3-aminophenoxy)phenyl] sulfide and pyromellitic dianhydride.

The above polyimide powder was dry blended with pellets of aromatic polyester, U-polymer U-100(Trade Mark of Unitika Co. Ltd.) in various compositions as illustrated in Table 1. The mixture obtained was melt kneaded at 340° to 360° C. with an extruder having a diameter of 40 mm and a screw of 3.0 in compression ratio, and extruded to cut into uniformly blended pellets.

The pellets obtained above were injection molded at a cylinder temperature of 370° C. and a mold temperature of 150° C. by using a conventional injection molding machine. Physical and thermal properties of molded specimens were measured. Results are illustrated in Table 1.

COMPARATIVE EXAMPLES 1 and 2

The same procedures as described in Examples 1-4 were carried out by using the compositions which were outside of the scope of the invention. Physical and thermal properties of the molded specimens were measured. Results are illustrated in Table 1.

EXAMPLES 5-7

Polyimide powder having an inherent viscosity of 0.50 dl/g, glass transition temperature of 257° C. and a melting point of 387° C. were prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride.

The above polyimide powder was dry blended with an aromatic polyester XYDAR SRT-500 (Trade Mark of DARTCO Co. Ltd.) which forms an anisotropic molten phase at a temperature of 420° C. or less, in various compositions as illustrated in Table 1. The mixtures obtained were melt-kneaded at 400° to 420° C. to obtain uniform pellets by carrying out the same procedures as described in Examples 1-4.

The pellets obtained were injection molded at a cylinder temperature of 400° to 420° C. and a mold temperature of 200° C. Physical and thermal properties of the molded specimens were tested and results are illustrated in Table 1.

COMPARATIVE EXAMPLES 3 AND 4

The same procedures as described in Examples 5-7 were carried out by using the compositions which were outside of the scope of the invention. Physical and thermal properties of the molded specimens were measured. Results are illustrated in Table 1.

EXAMPLES 8-10 AND COMPARATIVE EXAMPLES 5 AND 6

Polyimide powder having an inherent viscosity of 0.45 dl/g was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride. The polyimide powder was dry blended with aromatic polyether ketone VICTREX PEK 220P (Trade Mark of I.C.I. Ltd.) in compositions as illustrated in Table 2. The mixtures obtained were melt-kneaded with a twin screw extruder 30 mm in diameter at a cylinder temperature of 380° to 410° C. and extruded and cut into uniform pellets.

MFR of the pellets was measured and results are illustrated in Table 2.

The pellets were injection molded to obtain specimens having dimensions of 6 mm×70 mm×3 mm. HDT was measured on these specimens and results are illustrated in Table 2.

EXAMPLE 11 AND COMPARATIVE EXAMPLES 7 AND 8

Polyimide powder having an inherent viscosity of 0.46 dl/g was prepared from bis[4-(3-aminophenoxy)phenyl sulfide and pyromellitic dianhydride. The polyimide powder obtained was dry blended with aromatic polyether ketone VICTREX PEK 220P (Trade Mark of I.C.I. Ltd.) in the compositions as illustrated in Table 2. The mixtures obtained were evaluated by the same procedures as carried out in Example 8. Results are illustrated in Table 2.

EXAMPLE 12 AND COMPARATIVE EXAMPLES 9 AND 10

Polyimide powder having an inherent viscosity of 0.45 dl/g was prepared from 2,2-bis[4-(3-aminophenoxy)phenyl]propane and 3,3',4,4'-benzophenonetetracarboxylic dianhydride.

The polyimide powder obtained was dry blended with aromatic polyether ketone VICTREX PEK 220P(Trade Mark of I.C.I. Ltd.) in compositions as illustrated in Table 2. The mixtures obtained were evaluated by the same procedures as carried out in Example 8. Results are illustrated in Table 2.

EXAMPLES 13-17 AND COMPARATIVE EXAMPLES 11 AND 12

Polyimide having an inherent viscosity of 0.45 dl/g prepared from 4,4-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride. The polyimide obtained was dry blended with a thermotropic liquidcrystal polymer Xydar SRT-50 (Trade Mark of DARTCO CO. Ltd.) in compositions as illustrated in Table 3. The mixtures thus obtained were melt-kneaded in an extruder at a cylinder temperature of 400° C. and extruded and cut into pellets.

The pellets were injection molded at a cylinder temperature of 380° to 410° C., mold temperature of 190° C. and injection pressure of 500 kg/cm² to obtain tensile test specimens. Tensile test specimens having a weld at the center of the parallel portion were also injection molded under the same conditions. Results of tensile strength test are illustrated in Table 3.

Spiral flow length was measured at a cylinder temperature of 400° C., mold temperature of 180° C., injection pressure of 1000 kg/cm² and cavity thickness of 1 mm. Results are illustrated in Table 3.

Heat shrinkage, coefficient of linear expansion and peak temperature (Tc) of crystallization exotherm were measured by using injection molded tensile specimens without a weld. Results are illustrated in Table 3. The ratio TD/MD of the coefficient of linear thermal expansion was assumed as being anisotropic and are also illustrated in Table 3.

EXAMPLE 18

The same procedures as described in Example 14 were carried out except that ECONOL E-6000 (Trade Mark of Sumitomo Chemical Co. Ltd.) was used as a thermotropic liquid-crystal polymer. Results are illustrated in Table 3.

EXAMPLE 19

The same procedures as described in Example 16 were carried out except that ECONOL E-6000 (Trade Mark of Sumitomo Chemical Co. Ltd.) was used as a thermotropic liquid-crystal polymer.

COMPARATIVE EXAMPLE 13

The same procedures as described in Comparative Example 12 were carried out except that ECONOL E-6000 (Trade Mark of Sumitomo Chemical Co. Ltd.) was used as a thermotropic liquid-crystal polymer. Results are illustrated in Table 3.

EXAMPLE 20

The same procedures as described in Example 15 were carried out except that polyimide prepared from bis[4-(3-aminophenoxy)phenyl] sulfide and pyromellitic dianhydride and having an inherent viscosity of 0.46 dl/g was used. Results are illustrated in Table 3.

COMPARATIVE EXAMPLE 14

The same procedures as described in Comparative Example 11 were carried out except that polyimide prepared from bis[4-(3-aminophenoxy)phenyl]sulfide and pyromellitic dianhydride and having an inherent viscosity of 0.46 dl/g was used. Results are illustrated in Table 3.

COMPARATIVE EXAMPLE 15

The same procedures as described in Comparative Example 12 were carried out except that polyimide prepared from bis[4-(3-aminophenoxy)phenyl]sulfide and pyromellitic dianhydride and having an inherent viscosity of 0.46 dl/g was used. Results are illustrated in Table 3.

EXAMPLE 21

The same procedures as described in Example 15 were carried out except that polyimide prepared from 2,2-bis[4-(3-aminophenoxy)phenyl]propane and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and having an inherent viscosity of 0.45 dl/g was used. Results are illustrated in Table 3.

COMPARATIVE EXAMPLE 16

The same procedures as described in Comparative Example 11 were carried out except that polyimide prepared from 2,2-bis[4-(3-aminophenoxy)phenyl]propane and 3,3',4 4'-benzophenonetetracarboxylic dianhydride and having an inherent viscosity of 0.45 dl/g was used. Results are illustrated in Table 3.

COMPARATIVE EXAMPLE 17

The same procedures as described in Comparative Example 12 were carried out except that polyimide prepared from 2,2-bis[4-(3-aminophenoxy)phenyl] propane and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and having an inherent viscosity of 0.45 dl/g was used. Results are illustrated in Table 3.

                                      TABLE 1                                      __________________________________________________________________________                     Minimum         Izod impact                                               Aromatic                                                                            injection                                                                           Tensile                                                                             Elongation                                                                           strength                                                                              Heat distortion                         Polyimide  polyester                                                                           pressure*                                                                           strength                                                                            at break                                                                             (notched)                                                                             temperature                             (wt. part) (wt. part)                                                                          (kg/cm.sup.2)                                                                       (kg/cm.sup.2)                                                                       (%)   (kg · cm/cm)                                                                 (18.6 kg/cm.sup.2)                      __________________________________________________________________________                                            (°C.)                            Comp.                                                                               100    0   620  1650 60    21     215                                     Ex. 1                                                                          Example                                                                             95     5   540  1650 60    21     215                                     Example                                                                             85    15   450  1650 60    21     215                                     2                                                                              Example                                                                             75    25   380  1640 60    21     214                                     3                                                                              Example                                                                             50    50   330  1570 60    21     210                                     4                                                                              Comp.                                                                                0    100  300   720 55    20     175                                     Ex. 2                                                                          Comp.                                                                               100    2   750  1160 100   18     235                                     Ex. 3                                                                          Example                                                                             98     2   680  1160 100   18     243                                     5                                                                              Example                                                                             85    15   400  1150 97    18     276                                     6                                                                              Example                                                                             50    50   130  1100 87    17     316                                     7                                                                              Comp.                                                                                0    100  **    800  5     8     335                                     Ex. 4                                                                          __________________________________________________________________________      Note; *Lower melt viscosity causes lower minimum injection pressure.     

                                      TABLE 2                                      __________________________________________________________________________                           spiral                                                   Composition           flow                                                                               Heat Warpage                                         Polyimide  PEK  M F R length                                                                             shrinkage                                                                           *    H D T                                      (wt. %)    (wt. %)                                                                             (g/10 min)                                                                           (mm)                                                                               (%)  (%)  (°C.)                               __________________________________________________________________________     Example                                                                             90    10    9    65  6    22   225                                        Example                                                                             75    25   11    80  4    15   210                                        9                                                                              Example                                                                             60    40   14    105 2    10   200                                        10                                                                             Comp.                                                                               100    0    7    50  12   88   238                                        Ex. 5                                                                          Comp.                                                                               40    60   18    140 2     4   175                                        Ex. 6                                                                          Example                                                                             75    25   10    70  4    20   208                                        11                                                                             Comp.                                                                               100    0    5    30  14   96   232                                        Ex. 7                                                                          Comp.                                                                               40    60   16    120 3     6   170                                        Ex. 8                                                                          Example                                                                             75    25   10    65  4    18   210                                        12                                                                             Comp.                                                                               100    0    7    45  13   90   234                                        Ex. 9                                                                          Comp.                                                                               40    60   19    140 2     5   171                                        Ex. 9                                                                          __________________________________________________________________________      Note; *Injection molded plate (75 × 100 × 2 mm) is heat            treated and change of warpage height in longer direction was measured          between before and after treatment.                                      

                                      TABLE 3                                      __________________________________________________________________________                              Spiral    Coefficient of linear                               Composition      flow                                                                               Tc    thermal expansion                                                                          Anisot-                                                                             Tensile strength                   Polyimide                                                                            PEK  M F R length                                                                             (°C.)                                                                         (1/°C.)                                                                             ropy (kg/cm.sup.2)                      (wt. %)                                                                              (wt. %)                                                                             (g/10 min)                                                                           (mm)                                                                               Tc.sub.1                                                                          Tc.sub.2                                                                          TD    MD    TD/MD                                                                               Unwelded                                                                             Welded               __________________________________________________________________________     Example 13                                                                             Xydar  2    70   8   307                                                                               330                                                                               6.0 × 10.sup.-5                                                                5.6 × 10.sup.-5                                                                1.1  940   920                  Example 14                                                                             "      5    85   5   305                                                                               334                                                                               6.0 × 10.sup.-5                                                                5.0 × 10.sup.-5                                                                1.2  940   900                  Example 15                                                                             "     15   100   3   305                                                                               334                                                                               6.0 × 10.sup.-5                                                                4.0 × 10.sup.-5                                                                1.5  950   980                  Example 16                                                                             "     30   125   2   302                                                                               335                                                                               5.9 × 10.sup.-5                                                                3.0 × 10.sup.-5                                                                2.0  960   300                  Example 17                                                                             "     45   160   2   300                                                                               333                                                                               6.1 × 10.sup.-5                                                                2.5 × 10.sup.-5                                                                2.4  980   720                  Comp. Ex. 11                                                                           --    --    50   12  324                                                                               322                                                                               6.0 × 10.sup.-5                                                                6.0 × 10.sup.-5                                                                1.0  940   920                  Comp. Ex. 12                                                                           Xydar 60   190   1   299                                                                               333                                                                               6.6 × 10.sup.-5                                                                1.8 × 10.sup.-5                                                                3.7  960   580                  Example 18                                                                             ECONOL                                                                                5    90   6   306                                                                               331                                                                               6.0 × 10.sup.-5                                                                5.0 × 10.sup.-5                                                                1.2  930   870                  Example 19                                                                             "     30   135   4   302                                                                               332                                                                               6.1 × 10.sup.-5                                                                3.2 × 10.sup.-5                                                                1.9  940   720                  Comp. Ex. 13                                                                           "     60   200   1   300                                                                               333                                                                               7.0 × 10.sup.-5                                                                2.0 × 10.sup.-5                                                                3.5  950   510                  Example 20                                                                             Xydar 15    85   3   307                                                                               331                                                                               6.0 × 10.sup.-5                                                                4.1 × 10.sup.-5                                                                1.5  920   840                  Comp. Ex. 14                                                                           --    --    40   14  327                                                                               325                                                                               5.9 × 10.sup.-5                                                                5.9 × 10.sup.-5                                                                1.0  920   910                  Comp. Ex. 15                                                                           --    60   170   1   300                                                                               334                                                                               6.5 × 10.sup.-5                                                                1.8 × 10.sup.-5                                                                3.6  940   520                  Example 21                                                                             Xydar 15    90   3   306                                                                               330                                                                               6.0 × 10.sup.-5                                                                4.0 × 10.sup.-5                                                                1.5  900   830                  Comp. Ex. 16                                                                           --    --    45   12  325                                                                               323                                                                               6.0 × 10.sup.-5                                                                5.6 × 10.sup.-5                                                                1.0  910   900                  Comp. Ex. 17                                                                           "     60   180   1   300                                                                               331                                                                               6.0 × 10.sup.-5                                                                1.9 × 10.sup.-5                                                                3.6  930   500                  __________________________________________________________________________

EXAMPLES 22-27

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry blended with various ingredients in proportions illustrated in Table 1 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 400° C., injection pressure of 800 kg/cm² and a mold temperature of 180° to form specimens for measuring friction and wear characteristics, flexural strength, flexural modulus and softening temperature.

The inherent viscosity was measured at 35° C. by dissolving 0.5 g of polyimide powder in 100 ml of a solvent mixture of p-chlorophenol/phenol in a ratio of 90/10. Results obtained are illustrated in Table 4.

EXAMPLE 28

The same procedures as described in Example 23 were carried out except that polyimide which was prepared from bis[4-(3-aminophenoxy) phenyl] sulfide and pyromellitic anhydride and had an inherent viscosity of 0.46 dl/g was used. Results are illustrated in Table 4.

COMPARATIVE EXAMPLE 18-24

Specimens were prepared by carrying out the same procedures as described in Example 22 except that the raw materials were blended in proportions illustrated in Table 5. Properties of the specimens were measured, and results are illustrated in Table 5.

In Comparative Examples 18, 19 and 22, solid lubricant was added alone and phenolic resin was not added.

In Comparative Examples 20 and 21, solid lubricant and phenolic resin were added. However, the amounts of both additives were outside the scope of the invention.

In Comparative Example 23, phenolic resin was added alone in the absence of solid lubricant. Comparative Example 24 contains aromatic polyimide resin alone in the absence of phenolic resin and solid lubricant.

As seen in Table 4 and Table 5, any of Examples 22 to 28 illustrates stable and low friction coefficient and wear coefficient. In Comparative Examples 18˜24, either one or both of the coefficients have a very large value and clearly illustrate very inferior sliding property.

                  TABLE 4                                                          ______________________________________                                         Example     22     23     24   25   26   27   28                               ______________________________________                                         Formulation                                                                    Polyimide resin                                                                            95     95     95   70   70   70   95                               liquid crystal                                                                 polymer                                                                        Xydar       5      5      5    30   30   30   --                               ECONOL      --     --     --   --   --   --   5                                Bellpearl R-900                                                                            --     --     20   --   --   --   --                               Bellpearl C-2000                                                                           40     10     --   30   30   30   10                               PTFE        10     10     2    10   --   --   10                               Graphite    --     --     --   --   10   --   --                               Lead monoxide                                                                              --     --     --   --   --   10   --                               Physical properties                                                            Dynamic friction                                                                           0.22   0.24   0.22 0.20 0.23 0.24 0.23                             coefficient                                                                    Wear coefficient                                                                           80     35     50   35   60   40   40                               (10.sup.-10 cm.sup.3 /kg · m)                                         Flexural strength                                                                          13.8   13.5   14.3 14.0 12.1 11.8 13.2                             (kg/mm.sup.2)                                                                  Flexural modulus                                                                           370    340    390  370  440  290  340                              (kg/mm.sup.2)                                                                  Softening tempera-                                                                         240    238    241  239  240  234  238                              ture (°C.)                                                              ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                         Comparative                                                                    Example     18     19     20   21   22   23   24                               ______________________________________                                         Formulation                                                                    Polyimide resin                                                                            95     95     95   95   95   95   95                               liquid crystal                                                                 polymer                                                                        Xydar       5      5      5    5    5    5    5                                ECONOL      --     --     --   --   --   --   --                               Bellpearl C-2000                                                                           --     --     1    55   --   5    --                               PTFE        5      10     30   0.5  30   --   --                               Graphite    20     --     --   --   --   --                                    Lead monoxide                                                                              --     10     --   --   --   --   --                               Physical properties                                                            Dynamic friction                                                                           0.19   0.34   0.22 0.31 0.22 0.33 0.34                             coefficient                                                                    Wear coefficient                                                                           5100   75     7700 630  8500 1600 1900                             (10.sup.-10 cm.sup.3 /kg · m)                                         Flexural strength                                                                          12.0   11.5   9.0  9.8  8.8  11.6 12.7                             (kg/mm.sup.2)                                                                  Flexural modulus                                                                           530    300    210  480  200  320  320                              (kg/mm.sup.2)                                                                  Softening tempera-                                                                         238    233    230  237  229  235  229                              ture (°C.)                                                              ______________________________________                                    

In Table 4 and Table 5, thermotropic liquid crystals cured phenolic resin and solid lubricant which were used in Examples and Comparative Examples are as follows. Amounts in the formulation are parts by weight.

1 Thermotropic liquid crystal polymer:

Xydar SRT-500 (Trade mark; Nippon Oil Co.)

ECONOL E-6000 (Trade mark; Sumitomo Chemical Co.)

2 Phenolic resin

Bellpearl R-900 and C-2000 (Trade mark; Kanebo Co.)

Bellpearl R-900 has an average particle size of 48 μm and solubility of 5% by weight or less in methanol. Bellpearl C-2000 has an average particle size of 22 μm and solubility of 0.1% by weight or less in methanol. Lower solubility in methanol leads to better resistance to alcohol.

3 PTFE

KS-15 (Trade mark; Lonza Co.)

4 Graphite

ACP (Trade mark; Japan Graphite Co.)

5 Lead monoxide

Litharge S (Trade mark; Shinagawa Kako Co.)

EXAMPLES 29-38

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 6 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 410° C. , injection pressure of 900 kg/cm² and a mold temperature of 180° C. to form specimens measuring friction coefficient, flexural strength, dimensional change due to heat treatment accompanied with crystallization and threshold PV value. Results are illustrated in Table 6.

COMPARATIVE EXAMPLE 25˜28

Specimens were prepared by repeating the procedures of Example 29 except that the raw materials were blended in proportions illustrated in Table 7. Properties of the specimens were measured, and results are illustrated in Table 7.

EXAMPLES 39˜45

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 8 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 410° C., injection pressure of 900 kg/cm² and a mold temperature of 180° C. to form specimens for measuring friction coefficient, wear coefficient, dimensional change due to heat treatment accompanied with crystallization and threshold PV value. Results are illustrated in Table 8.

COMPARATIVE EXAMPLE 29˜32

Specimens were prepared by repeating the procedures of Example 39 except that the raw materials were blended in proportions illustrated in Table 9. Properties of the specimens were measured, and results are illustrated in Table 9.

As seen by comparing Table 6 and Table 8 with Table 7 and Table 9, any of Examples 29˜45 have a stable and low friction coefficient and good dimensional stability after treatment, and can improve threshold PV value. On the other hand, Comparative Examples 25˜33 are definitely very poor in either one of those properties or have a disadvantage of very large decrease in mechanical strength.

                  TABLE 6                                                          ______________________________________                                         Example     29     30     31   32   33   34   35                               ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                            95     95     95   90   90   80   80                               Liquid crystal                                                                 polymer                                                                        ECONOL      5      5      --   10   10   --   20                               Xydar       --     --     5    --   --   20   --                               Vectra      --     --     --   --   --   --   --                               PTFE        5      10     10   10   10   5    10                               Graphite    --     15     30   15   30   0    30                               Aromatic polyamide                                                                         --     --     --   --   --   --   --                               resin                                                                          Physical properties                                                            Dynamic friction                                                                           0.15   0.12   0.11 0.11 0.10 0.14 0.10                             coefficient                                                                    Dimensional                                                                    stability                                                                      TD (%)      -1.1   -1.0   -1.0 -0.1 -0.1 -0.2 -0.1                             MD (%)      -1.0   -0.9   -0.9 -0.2 -0.2 -0.2 -0.2                             Limit of PV value                                                              untreated   1200   1400   1400 1400 1400 1200 1400                             heat treated                                                                               1400   1600   1600 1600 1600 1400 1600                             (kg/cm.sup.2 · m/min)                                                 Flexural strength                                                                          12.4   12.1   11.7 13.1 12.8 13.6 12.9                             (kg/mm.sup.2)                                                                  ______________________________________                                         Example           36       37       38                                         ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin   50       90       90                                         Liquid crystal polymer                                                         ECONOL            --       --       --                                         Xydar             50       10       --                                         Vectra            --       --       10                                         PTFE              --       17       31                                         Graphite          5        45       15                                         Aromatic polyamide                                                                               --       --       --                                         resin                                                                          Physical properties                                                            Dynamic friction  0.20     0.10     0.10                                       coefficient                                                                    Dimensional stability                                                          TD (%)            -0.2     -0.2     -0.2                                       MD (%)            -0.2     -0.3     -0.3                                       Limit of PV value                                                              untreated         1200     1400     1400                                       heat treated      1400     1400     1600                                       (kg/cm.sup.2 · m/min)                                                 Flexural strength 13.7     11.7     11.0                                       (kg/mm.sup.2)                                                                  ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                         Comparative Example                                                                           25      26      27     28                                       ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                               95      90      100    100                                      Liquid crystal polymer                                                         ECONOL         5       10      --     --                                       Xydar          --      --      --     --                                       Vectra         --      --      --     --                                       PTFE           --      60      11     21                                       Graphite       --      60      21     --                                       Aromatic polyamide                                                                            --      --      --     --                                       resin                                                                          Physical properties                                                            Dynamic friction                                                                              0.38    0.10    0.14   0.15                                     coefficient                                                                    Dimensional stability                                                          TD (%)         -1.1    -0.4    -29.4  -29.6                                    MD (%)         -1.0    -0.5    -31.6  -32.1                                    Limit of PV value                                                              untreated      1200    1200    1200   1400                                                                    (a)    (a)                                      heat treated   1200    1400    --     --                                       (kg/cm.sup.2 · m/min)                                                 Flexural strength                                                                             12.7    8.5     7.8    7.8                                      (kg/mm.sup.2)                                                                  ______________________________________                                          Note: (a) Heat treatment caused severe warpage Measurement was impossible

                  TABLE 8                                                          ______________________________________                                         Example     39     40     41   42   43   44   45                               ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                            90     90     90   75   75   75   70                               Liquid crystal                                                                 polymer                                                                        ECONOL      10     10     --   25   --   --   30                               Xydar       --     --     10   --   25   --   --                               Vectra      --     --     --   --   --   25   --                               PTFE        5      10     30   5    10   50   30                               Graphite    --     --     --   --   --   --   30                               Aromatic polyamide                                                                         5      10     30   10   20   50   30                               resin                                                                          Physical properties                                                            Dynamic friction                                                                           0.25   0.25   0.18 0.26 0.28 0.14 0.20                             coefficient                                                                    Dimensional                                                                    stability                                                                      TD (%)      -0.1   -0.1   -0.2 -0.1 -0.1 -0.2 -0.1                             MD (%)      -0.2   -0.2   -0.3 -0.2 -0.2 -0.3 -0.2                             Limit of PV value                                                              untreated   1200   1400   2200 1200 2000 2200 2400                             heat treated                                                                               1400   1600   2600 1400 2400 2600 2600                             (kg/cm.sup.2 ·  m/min)                                                Wear coefficient                                                                           360    170    60   340  200  110  10                               (× 10.sup.-8 cm.sup.3 min/                                               kgmHr)                                                                         ______________________________________                                    

                  TABLE 9                                                          ______________________________________                                         Comparative Example                                                                             29      30      31   32                                       ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin  85      98      98   100                                      Liquid crystal polymer                                                         ECONOL           15      2       --   --                                       Xydar            --      --      2    --                                       Vectra           --      --      --   --                                       PTFE             --      80      55   --                                       Graphite         --      --      55   --                                       Aromatic polyamide                                                                              --      80      70   10                                       resin                                                                          Physical properties                                                            Dynamic friction 0.35    (b)     (b)  0.30                                     coefficient                                                                    Dimensional stability                                                          TD (%)           -0.1                 -28.8                                    MD (%)           -0.2                 -30.1                                    Limit of PV value                                                              untreated        1200                 600                                                                            (a)                                      heat treated     1200                 --                                       (kg/cm.sup.2 · m/min)                                                 Wear coefficient 1400                 1110                                     (× 10.sup.-8 cm.sup.3 min/kgmHr)                                         ______________________________________                                          Note: (a) Heat treatment caused severe warpage and measurement was             impossible                                                                     (b) Processing was impossible.                                           

In Tables 6˜9, thermotropic liquid crystals, fluororesin, graphite and aromatic polyamide resin which were used in Examples and Comparative Examples are as follows.

(1) Thermotropic liquid crystal polymer

Xydar SRT-500 (Trade mark; Nippon Oil Co.)

ECONOL E-6000 (Trade mark; Sumitomo Chemical Co.)

Vectra A-950 (Trade mark; Polyplastics Co.)

(2) Fluororesin

PTFE L-5 (Trade mark; Dankin Co.)

(3) Graphite:

ACP (Trade mark; Japan Graphite Co.) (4) Aromatic polyamide resin

KEVLAR 49 (Trade mark; E.I.Du Pont de Nemours &. Co.)

EXAMPLES 46˜54

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 10 and extruded through a twin-screw extruder at 370° to 400 T to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 410° C., injection pressure of 900 kg/cm² and a mold temperature of 180° C. to form specimens. Tensile strength, tensile modulus and flexural modulus were measured by those specimens. The pellets were injection molded at a cylinder temperature of 420° C., injection pressure of 1500 kg/cm^(a) and mold temperature of 180° C. to measure spiral flow length having a flow thickness of 1 mm. Results are illustrated in Table 10.

COMPARATIVE EXAMPLE 33˜36

Specimens were prepared by repeating the procedures of Example 46 except that the raw materials were blended in proportions illustrated in Table 11. Properties of the specimens were measured, and results are illustrated in Table 11.

As clearly understood by comparing Table 10 and Table 11, any of Examples 46-54 have excellent mechanical properties and processability. On the other hand, Comparative Examples 33-36 have disadvantage that either mechanical properties or processability are inferior.

                  TABLE 10                                                         ______________________________________                                         Example        46     47     48   49   50   51                                 ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                               98     96     94   90   87   85                                 Liquid crystal polymer                                                         ECONOL         --     4      --   --   13   --                                 Xydar          2      --     --   10   --   15                                 Vectra         --     --     6    --   --   --                                 Carbon fiber   45     45     45   45   45   55                                 Glass fiber    6      --     --   --   --   --                                 Physical properties                                                            Tensile strength                                                                              25.0   25.5   25.0 25.0 24.8 25.4                               (kg/mm.sup.2)                                                                  Tensile modulus                                                                               2.1    2.1    2.3  2.4  2.5  2.5                                (10.sup.3 kg/mm.sup.2)                                                         Flexural modulus                                                                              2.1    2.1    2.2  2.3  2.3  2.3                                (10.sup.3 kg/mm.sup.2)                                                         Spiral flow length                                                                            40     42     45   59   70   50                                 (mm)                                                                           ______________________________________                                         Example           52       53       54                                         ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin   80       70       60                                         Liquid crystal polymer                                                         ECONOL            20       --       --                                         Xydar             --       30       40                                         Vectra            --       --       --                                         Carbon fiber      55       60       65                                         Glass fiber       --       5        --                                         Physical properties                                                            Tensile strength  25.2     25.3     25.1                                       (kg/mm.sup.2)                                                                  Tensile modulus   2.5      2.5      2.5                                        (10.sup.3 kg/mm.sup.2)                                                         Flexural modulus  2.3      2.3      2.3                                        (10.sup.3 kg/mm.sup.2)                                                         Spiral flow length                                                                               55       50       56                                         (mm)                                                                           ______________________________________                                    

                  TABLE 11                                                         ______________________________________                                         Comparative Example                                                                             33      34      35    36                                      ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin  100     100     100   100                                     Liquid crystal polymer                                                         ECONOL           --      --      --    --                                      Xydar            --      --      20    --                                      Vectra           --      --      --    15                                      Carbon fiber     --      45      --    110                                     Glass fiber      --      --      --    --                                      Physical properties                                                            Tensile strength 9.4     23.3    9.9   (a)                                     (kg/mm.sup.2)                                                                  Tensile modulus  0.3     1.9     0.4                                           (10.sup.3 kg/mm.sup.2)                                                         Flexural modulus 0.3     1.9     0.4                                           (10.sup.3 kg/mm.sup.2)                                                         Spiral flow length                                                                              80      35      250                                           (mm)                                                                           ______________________________________                                          Note; (a) Processing was impossible.                                     

The following thermotropic liquid crystal polymers and carbon fiber were used in Table 11 and Table 12.

(1) Thermotropic liquid crystal polymer:

Xydar SRT-500 (Trade mark; Nippon Oil Co.)

ECONOL E-6000 (Trade mark; Sumitomo Chemical Co.)

Vectra A-950 (Trade mark; Polyplastics Co.)

(2) Carbon fiber

Carbon fiber HTA (Trade mark; Toho Rayon Co.)

EXAMPLES 55˜61

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 12 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 410° C., injection pressure of 900 kg/cm² and a mold temperature of 180° C. to form specimens.

Molding shrinkage, tensile strength, flexural strength and heat distortion temperature were measured by these specimens. Results are illustrated in Table 12.

EXAMPLE 62

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 12 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 420° C., injection pressure of 1500 kg/cm² and a mold temperature of 180° C. to measure spiral flow length having a thickness of 1 mm.

EXAMPLES 37˜40

Specimens were prepared by repeating the procedures of Example 55 except that the raw materials were blended in proportions illustrated in Table 13. Properties of the specimens were measured, and results are illustrated in Table 13.

COMPARATIVE EXAMPLE 41

Various raw materials were blended with formulations illustrated in Table 14 and spiral flow length was measured by carrying out the same procedures as described in Example 62. Results are illustrated in Table 14.

As seen in Table 12 and Table 13, any of Examples 55˜61 exhibit excellent mechanical properties and molding shrinkage. On the other hand, Comparative Examples 37˜40 have disadvantage that either mechanical properties or molding shrinkage is distinctly inferior.

As seen in Table 14, Example 62 has excellent processability. On the other hand, Comparative Example 41 is short in the spiral flow length and hence is inferior in processability.

                  TABLE 12                                                         ______________________________________                                         Example     55     56     57   58   59   60   61                               ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                            90     90     90   90   80   80   80                               Liquid crystal                                                                 polymer                                                                        ECONOL      10     10     --   --   20   --   --                               Xydar       --     --     10   10   --   --   20                               Vectra      --     --     --   --   --   20   --                               Potassium   10     30     50   70   80   100  150                              titanate fiber                                                                 Physical properties                                                            Molding shrinkage                                                              MD (%)      0.4    0.2    0.2  0.2  0.2  0.1  0.1                              TD (%)      0.5    0.3    0.3  0.2  0.2  0.1  0.1                              Tensile strength                                                                           12.2   13.9   14.7 16.3 16.9 18.0 19.6                             (kg/mm.sup.2)                                                                  Flexural strength                                                                          16.3   18.0   20.0 22.1 22.9 24.9 25.9                             (kg/mm.sup.2)                                                                  Heat distortion                                                                            235    240    243  246  247  250  251                              temperature (°C.)                                                       ______________________________________                                    

                  TABLE 13                                                         ______________________________________                                         Comparative Example                                                                             37      38      39    40                                      ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin  100     95      70    90                                      Liquid crystal polymer                                                         ECONOL           --      5       --    --                                      Xydar            --      --      30    10                                      Vectra           --      --      --    --                                      Potassium        --      --      --    220                                     titanate fiber                                                                 Physical properties                                                            Molding shrinkage                                                              MD (%)           0.8     0.6     0.4   (a)                                     TD (%)           0.8     0.7     0.7                                           Tensile strength 9.4     10.0    9.8                                           (kg/mm.sup.2)                                                                  Flexural strength                                                                               14.0    14.9    14.8                                          (kg/mm.sup.2)                                                                  Heat distortion  235     235     235                                           temperature (°C.)                                                       ______________________________________                                          Note; (a) Processing was impossible                                      

                  TABLE 14                                                         ______________________________________                                                                Comparative                                                            Example 62                                                                             Example 41                                              ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin  70        100                                                 Liquid crystal polymer                                                         ECONOL           30        --                                                  Xydar            --        --                                                  Vectra           --        --                                                  Potassium titanate                                                                              80        80                                                  fiber                                                                          Spiral flow length (mm)                                                                         55         7                                                  ______________________________________                                    

In Tables 12˜14, the following thermotropic liquid crystal polymers and potassium titanate fiber were used.

(1) Thermotropic liquid crystal polymer

Xydar SRT-500 (Trade mark; Nippon Oil Co.)

ECONOL E-6000 (Trade mark; Sumitomo Chemical Co.)

Vectra A-950 (Trade mark; Polyplastics Co.)

(2) Potassium titanate fiber

Potassium titanate whisker TISMO-D (Trade mark; Ohtsuka Chemical Co.)

EXAMPLES 63˜76

Polyimide which was prepared from 4,4'-bis(3-aminophenoxy) biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.46 dl/g was dry blended with various ingredients in proportions illustrated in Table 12 and extruded through a twin-screw extruder at 370° to 400° C. to form pellets. The pellets were injection molded at a cylinder temperature of 370° to 410° C. , injection pressure of 900 kg/cm² and a mold temperature of 180° C. to form specimens.

Friction coefficient, wear coefficient, tensile strength and flexural strength were measured. Results are illustrated in Table 15 and Table 16.

COMPARATIVE EXAMPLE 42˜46

Specimens were prepared by repeating the procedures of Example 63 except that the raw materials were blended in proportions illustrated in Table 17. Properties of the specimens were measured, and results are illustrated in Table 17.

                  TABLE 15                                                         ______________________________________                                         Example     63     64     65   66   67   68   69                               ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                            90     90     90   90   90   90   90                               Liquid crystal                                                                 polymer                                                                        ECONOL      10     10     10   --   --   --   --                               Xydar       --     --     --   10   10   10   --                               Vectra      --     --     --   --   --   --   10                               PTFE        30     40     10   10   20   20   50                               Carbon fiber                                                                               60     65     40   50   55   40   70                               Physical properties                                                            Dynamic friction                                                                           0.14   0.14   0.16 0.16 0.16 0.16 0.13                             coefficient                                                                    Wear coefficient                                                                           180    180    200  190  180  200  170                              (× 10.sup.-8 cm.sup.3 min/                                               kgmhr)                                                                         Tensile strength                                                                           24.0   23.7   20.9 24.8 24.5 20.4 23.1                             (kg/mm.sup.2)                                                                  Flexural strength                                                                          19.0   18.5   16.5 20.1 19.4 16.2 17.8                             (kg/mm.sup.2)                                                                  ______________________________________                                    

                  TABLE 16                                                         ______________________________________                                         Example     70     71     72   73   74   75   76                               ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                            75     75     70   70   70   70   70                               Liquid crystal                                                                 polymer                                                                        ECONOL      25     --     30   30   --   --   --                               Xydar       --     25     --   --   30   30   --                               Vectra      --     --     --   --   --   --   30                               PTFE        15     20     30   40   10   20   50                               Carbon fiber                                                                               40     40     60   65   50   55   70                               Physical properties                                                            Dynamic friction                                                                           0.16   0.16   0.14 0.14 0.15 0.15 0.13                             coefficient                                                                    Wear coefficient                                                                           180    180    170  170  180  180  170                              (× 10.sup.-8 cm.sup.3 min/                                               kgmhr)                                                                         Tensile strength                                                                           19.1   18.9   23.0 22.2 24.0 23.3 21.9                             (kg/mm.sup.2)                                                                  Flexural strength                                                                          15.8   15.6   18.1 17.9 19.6 18.8 16.9                             (kg/mm.sup.2)                                                                  ______________________________________                                    

                  TABLE 17                                                         ______________________________________                                         Comparative Example                                                                          42      43      44    45    46                                   ______________________________________                                         Formulation                                                                    (wt %)                                                                         Polyimide resin                                                                              100     95      80    90    70                                   Liquid crystal polymer                                                         ECONOL        --      --      --    --    30                                   Xydar         --      5       20    --    --                                   Vectra        --      --      --    10    --                                   PTFE          --      --      85    10    70                                   Carbon fiber  --      --      40    200   170                                  Physical properties                                                            Dynamic friction                                                                             0.41    0.38    0.13  (a)   0.13                                 coefficient                                                                    Wear coefficient                                                                             1700    1400    110         90                                   (× 10.sup.-8 cm.sup.3 min/                                               kgmhr)                                                                         Tensile strength                                                                             9.4     9.9     7.1         8.1                                  (kg/mm.sup.2)                                                                  Flexural strength                                                                            13.1    12.7    10.2        10.9                                 (kg/mm.sup.2)                                                                  ______________________________________                                          Note; (a); Processing was impossible                                     

In Tables 15˜17, following thermotropic liquid crystal polymer, fluororesin and carbon fiber were used.

(1) Thermotropic liquid crystal polymer

Xydar SRT-500 (Trade mark; Nippon Oil Co.)

ECONOL E-6000 (Trade mark; Sumitomo Chemical Co.)

Vectra A-950 (Trade mark; Polyplastics Co.)

(2) Fluororesin

PTFE 1-5 (Trade mark; Dankin Co.)

(3) Carbon fiber

Carbon fiber HTA (Trade mark; Toho Rayon Co.)

As seen in Tables 15˜17, any of Examples 63˜76 exhibit excellent sliding property and mechanical properties. On the other hand, Comparative Examples 42˜46 are very poor in either one of these properties or have distinctly inferior processability.

Preparation Example of Polyimide

To a reaction vessel equipped with a stirrer, reflux condenser and a nitrogen inlet tube, 21.8 kg (100 mole) of pyromellitic dianhydride and 38.3 kg of N,N'-dimethylacetamide was charged. To the solution, 35.7 kg (97 mole) of 4,4'-bis(3-aminophenoxy)biphenyl was added by portions with caution to prevent temperature rise of the solution and stirred for 20 hours at the room temperature.

Successively 2.0 kg (20 mole) of triethylamine and 25.5 kg (25 mole) of acetic anhydride were added dropwise. After an hour from finishing dropwise addition, yellow polyimide powder started to precipitate. Stirring was continued for further 10 hours at room temperature. Resulting slurry was filtered, washed with methanol and dried at 180° C. for 2 hours-to obtain 51.1 kg of polyimide powder having an inherent viscosity of 0.62 dl/g. The inherent viscosity was measured at 35° C. in a solution containing 0.5 g of polyimide in 100° C. of a solvent mixture of p-chlorophenol/phenol in a weight ratio of 90/10.

EXAMPLES 77˜80

Polyimide resin powder which was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry-blended with crystallization accelerator CaCl₂ in formulations illustrated in Table 18 and pelletized by an extruder having a bore diameter of 40 mm at a cylinder temperature of 360° to 410° C.

The crystallization velocity of the resulting pellet was examined with a Parkin-Elmer differential scanning calorimeter (hereinafter referred to as DSC). About 10 mg of the sample was completely melted by heating at 400° C. for 5 minutes and successively cooled at a rate of 16° C./min to measure crystallization temperature and calorific value at the crystallization.

EXAMPLES 81˜84

The same procedures as described in Examples 77˜80 were carried out except that aluminum phosphate was used as a crystallization accelerator. Results are illustrated in Table 18.

EXAMPLES 85˜88

The procedures of Examples 77˜80 were repeated except that hydrotalcite compounds were used as a crystallization accelerator. Results are illustrated in Table 18.

EXAMPLES 89-99

The same procedures as described in Examples 77-80 were carried out except that Nal was used as a crystallization accelerator. Results are illustrated in Table 18.

COMPARATIVE EXAMPLES 47˜52

The same procedures as described in Examples 77˜80 were carried out on the systems without crystallization accelerators and the systems having 30 parts by weight of various crystallization accelerators. Results are illustrated in Table 18.

In DSC analysis, a higher exothermic peak generally means a faster rate of crystallization. The system without a crystallization accelerator has a slow rate of crystallization and thus generates almost no exothermic heat. On the other hand, the systems containing various crystallization accelerators have increased exothermic heat which indicates enhanced rate of crystallization.

However, when the amount of the crystallization accelerator is 30 parts by weight, melt flowability is severely decreased and leads to problems such as impaired processability.

EXAMPLES 97-100

Polyimide resin powder which was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry-blended with a compound-I having the formula: ##STR34## as a crystallization accelerator in formulations illustrated in Table 19 and pelletized by an extruder having a bore diameter of 10 mm at a cylinder temperature of 360° to 410° C.

The crystallization velocity of the resulting pellets was examined with a Parkin-Elmer differential scanning calorimeter (hereinafter referred to as DSC). About 10 mg of the sample was completely melted by heating at 400° C. for 5 minutes and successively cooled at a rate of 16° C./min to measure crystallization temperature and calorific value at the crystallization.

The pellet obtained above was injection molded at a cylinder temperature of 370° to 420° C. to form tensile test specimens. The mechanical properties of the specimens were measured in accordance with ASTM D-638 and results are illustrated in Table 19.

EXAMPLES 101˜104

The same procedures as described in Examples 97˜100 were carried out except that an imide oligomer-I having the formula: ##STR35## was used as a crystallization accelerator. Results are illustrated in Table 19.

EXAMPLES 105˜108

The same procedures as described in Examples 97˜100 were carried out except that an imide oligomer-II having the formula: ##STR36## was used as a crystallization accelerator. Results are illustrated in Table 19.

COMPARATIVE EXAMPLES 53˜56

The same procedures as described in Examples 97˜100 were carried out on the systems without crystallization accelerators and the systems having 30 parts by weight of various crystallization accelerators. Results are illustrated in Table 19.

In DSC analysis, a higher exothermic peak generally means faster rate of crystallization. The system without a crystallization accelerator has a slow rate of crystallization and thus generates almost no exothermic heat. On the other hand, the systems containing various crystallization accelerators have much increased exothermic heat which indicates enhanced rate of crystallization.

However, when the amount of the crystallization accelerator is 30 parts by weight, melt flowability is severely decreased and leads to problems such as a great decrease in mechanical strength.

EXAMPLES 109˜113

Polyimide resin powder which was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry blended with an aromatic polyester, Xydar SRT-500 (Trade mark; DARTCO Co.) which formed an anisotropic molten phase at a temperature of 420° C. or less and CaCl₂ as a crystallization accelerator in formulations illustrated in Table 20. The formulations were pelletized with an extruder having a bore diameter of 40 mm at a cylinder temperature of 360° to 410° C.

The pellet obtained was injection molded at a cylinder temperature of 380° to 420° C. , mold temperature of 190 T and injection pressure of 500 kg/cm² to obtain tensile test specimens. Further, tensile test specimens having a weld at the center of the parallel portion were injection molded by the same procedures as above. Tensile strength of these specimens were measured and results are illustrated in Table 20. A spiral flow length with a melt-flow thickness of 1 mm was measured by injection molding the pellet at a cylinder temperature of 400° C. , mold temperature of 180° C. and injection pressure of 1000 kg/cm². Results are illustrated in Table 20.

EXAMPLES 114˜115

The same procedures as conducted in Examples 109˜113 were carried out except that ECONOL E-6000 which was manufactured by Sumitomo Chemical Co. was used as a thermotropic liquid crystal polymer. Results are illustrated in Table 20.

EXAMPLES 116˜117

The same procedures as described in Examples 109˜113 were carried out except that Vectra A-950 which was manufactured by Polyplastics Co. was used as a thermotropic liquid crystal polymer. Results are illustrated in Table 20.

COMPARATIVE EXAMPLE 57˜59

The procedures carried out in Examples 109˜113 were repeated except that the amount of each thermotropic liquid crystal polymer was changed as illustrated in Table 20. Results are illustrated in Table 20.

A seen in the results of spiral flow length illustrated in Table 20, flowability is much improved by using 1 part by weight or more of the thermotropic liquid crystal polymer. However, in the case of 50 parts by weight or more of the thermotropic liquid crystal polymer weld strength is seriously decreased.

EXAMPLES 118˜121

Polyimide resin powder which was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry-blended with aromatic polyester, Xydar SRT-500 (Trade mark; DARTCO Co.) which formed an anisotropic molten phase at a temperature of 420° C. or less and CaCl₂ as a crystallization accelerator in formulations illustrated in Table 19 and pelletized by an extruder having a bore diameter of 40 mm at a cylinder temperature of 360° to 410° C.

The crystallization velocity of the resulting pellet was examined with a Parkin-Elmer differential scanning calorimeter (hereinafter referred to as DSC). About 10 mg of the sample was completely melted by heating at 400° C. for 5 minutes and successively cooled at a rate of 16° C./min to measure crystallization temperature and calorific value at the crystallization.

The pellet obtained above was injection molded at a cylinder temperature of 380°˜420° C., mold temperature of 190° C. and injection pressure of 500 kg/cm² to form tensile test specimens. Results on the mechanical strength measurement are illustrated in Table 21.

EXAMPLES 122-125

The same procedures as described in Examples 118˜121 were carried out except that aluminum phosphate was used as a crystallization accelerator. Results are illustrated in Table 21.

EXAMPLES 126˜129

The procedures of Examples 118˜121 were repeated except that hydrotalcite compounds were used as a crystallization accelerator. Results are illustrated in Table 21.

EXAMPLES 130˜133

The same procedures as described in Examples 118˜121 were carried out except that NaCl was used as a crystallization accelerator. Results are illustrated in Table 21.

EXAMPLES 134˜137

The procedures of Examples 118˜121 were repeated except that graphite was used as a crystallization accelerator. Results are illustrated in Table 21.

COMPARATIVE EXAMPLE 60˜65

The same procedures as described in Examples 118˜121 were carried out on the systems without crystallization accelerators and the systems having 30 parts by weight of various crystallization accelerators. Results are illustrated in Table 21.

In DSC analysis, a higher exothermic peak generally means a faster rate of crystallization. The system without a crystallization accelerator has a slow rate of crystallization and thus generates almost no exothermic heat. On the other hand, the systems containing various crystallization accelerators have much increased exothermic heat which indicates enhanced rate of crystallization.

However, when the amount of the crystallization accelerator is 30 parts by weight, melt flowability is severely decreased and leads to problems such as a great decrease in mechanical strength.

EXAMPLES 138˜142

Polyimide resin powder which was prepared from 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g dry blended with an aromatic polyester, Xydar SRT-500 (Trade mark; DARTCO Co.) which formed an anisotropic molten phase at a temperature of 420° C. or less and Compound-I which was used in Examples 97˜100, as a crystallization accelerater in formulations illustrated in Table 22. The formulations were pelletized with an extruder having a bore diameter of 40 mm at a cylinder temperature of 360° to 410° C. ##STR37##

The pellet obtained was injection molded at a cylinder temperature of 380° to 420° C., mold temperature of 190° C. and injection pressure of 500 kg/cm² to obtain tensile test specimens. Further, tensile test specimens having a weld at the center of the parallel portion were injection molded by the same procedures as above. Tensile strength of these specimens were measured and results are illustrated in Table 22. A spiral flow length with a melt-flow thickness of 1 mm was measured by injection molding the pellet at a cylinder temperature of 400° C., mold temperature of 180° C. and injection pressure of 1000 kg/cm². Results are illustrated in Table 22.

EXAMPLES 143˜144

The same procedures as conducted in Examples 138˜142 were carried out except that ECONOL E-6000 which was manufactured by Sumitomo Chemical Co. was used as a thermotropic liquid crystal polymer. Results are illustrated in Table 22.

EXAMPLES 145˜146

The same procedures as described in Examples 1384142 were carried out except that Vectra A-950 which was manufactured by Polyplastic Co. was used as a thermotropic liquid crystal polymer. Results are illustrated in Table 22.

COMPARATIVE EXAMPLE 66˜68

The procedures carried out in Examples 138˜142 were repeated except that the amount of each thermotropic liquid crystal polymer was changed as illustrated in Table 22. Results are illustrated in Table 22.

As seen in the results of spiral flow length illustrated in Table 22, flowability is much improved by using 1 part by weight or more of the thermotropic liquid crystal polymer. However, 50 parts by weight or more of the thermotropic liquid crystal polymer seriously lowers weld strength.

EXAMPLES 147˜150

Polyimide resin powder which was prepared from 4,4'-bis(3-ammophenoxy)biphenyl and pyromellitic dianhydride and had an inherent viscosity of 0.45 dl/g was dry-blended with aromatic polyester, Xydar SRT-500 (Trade mark; DARTCO Co.) which formed an anisotropic molten phase at a temperature of 420° C. or less and Compound-I which was used in Examples 97-100 as a crystallization accelerator, in formulations illustrated in Table 23 and pelletized by an extruder having a bore diameter of 40 mm at a cylinder temperature of 360° to 410° C. ##STR38##

The crystallization velocity of the resulting pellet was examined with a Parkin-Elmer DSC. About 10 m9 of the sample was completely melted by heating at 400° C. for 5 minutes and successively cooled at a rate of 16° C./min to measure crystallization temperature and calorific value at the crystallization. Results are illustrated in Table 23.

The pellet obtained above was injection molded at a cylinder temperature of 380°-420° C., mold temperature of 190° C. and injection pressure of 500 kg/cm² to form tensile test specimens. Results on the mechanical strength measurement are illustrated in Table 23.

EXAMPLES 151˜157

The same procedures as conducted in Example 147˜150 were carried out except that the imide oligomer-I used in Examples 101˜104 was used as a crystallization accelerator. Results are illustrated in Table 23. ##STR39##

EXAMPLES 155˜158

The same procedures as conducted in Example 147˜150 were carried out except that the imide oligomer-II used in Examples 105˜108 was used as a crystallization accelerator. Results are illustrated in Table 23. ##STR40##

COMPARATIVE EXAMPLE 69˜72

The same procedures as described in Examples 147˜150 were carried out on the systems without crystallization accelerators and the systems having 30 parts by weight of various crystallization accelerators. Results are illustrated in Table 23.

In DSC analysis, a higher exothermic peak generally means a faster rate of crystallization. The system without a crystallization accelerator has a slow rate of crystallization and thus leads to almost no heat generation. On the other hand, the systems containing various crystallization accelerators have much increased heat generation which indicates enhanced rate of crystallization.

However, when the amount of the crystallization accelerator is 30 parts by weight, melt flowability is severely decreased and leads to problems such as a great decrease in mechanical strength.

                  TABLE 18                                                         ______________________________________                                                          D S C                                                                            Crystalli-                                                         Crystalization                                                                             zation   Heat                                                      accelerator tempera- generat- MI                                               Com-   Amount   ture     ion    (g/10                                          pound  (wt part)                                                                               (°C.)                                                                            (cal/g)                                                                               min)                                    ______________________________________                                         Comp. Ex. 47                                                                            --       --       295    0.7    24.0                                  Example 77                                                                              CaCl.sub.2                                                                              0.5      296    2.4    24.0                                  Example 78                                                                              "        1        298    4.0    22.1                                  Example 79                                                                              "        5        298    3.8    18.3                                  Example 80                                                                              "        15       300    4.5    16.5                                  Comp. Ex. 48                                                                            "        30       302    4.7    11.2                                  Example 81                                                                              AlPO.sub.4                                                                              0.5      295    1.5    24.0                                  Example 82                                                                              "        1        296    1.8    23.0                                  Example 83                                                                              "        5        297    2.3    18.1                                  Example 84                                                                              "        15       298    2.7    15.8                                  Comp. Ex. 49                                                                            "        30       298    2.9    12.4                                  Example 85                                                                              hydro-   0.5      298    3.1    24.0                                           talcite                                                               Example 86                                                                              hydro-   1        300    4.1    22.0                                           talcite                                                               Example 87                                                                              hydro-   5        307    4.5    17.1                                           talcite                                                               Example 88                                                                              hydro-   15       312    4.8    14.3                                           talcite                                                               Comp. Ex. 50                                                                            hydro-   30       315    4.8    8.7                                            talcite                                                               Example 89                                                                              NaCl     0.5      296    2.1    24.0                                  Example 90                                                                              "        1        301    3.1    21.0                                  Example 91                                                                              "        5        303    3.2    16.3                                  Example 92                                                                              "        15       305    3.5    13.8                                  Comp. Ex. 51                                                                            "        30       305    3.6    5.1                                   Example 93                                                                              graphite 0.5      295    1.3    24.0                                  Example 94                                                                              "        1        297    1.6    21.3                                  Example 95                                                                              "        5        299    2.1    17.0                                  Example 96                                                                              "        15       302    2.4    12.1                                  Comp. Ex. 52                                                                            "        30       304    2.7    7.2                                   ______________________________________                                          Note                                                                           CaCl.sub.2 : Kanto Kagaku Co.                                                  AlPO.sub.4 : Junsei Kagaku Co.                                                 hydrotalcite: DHT4A.sub.2, Kagawa Kagaku Kogyo Co.                             NaCl: Junsei Kagaku Co.                                                        graphite: Lonza Japan Co.                                                

                                      TABLE 19                                     __________________________________________________________________________             Crystalization                                                                              D S C                                                             accelerater  Crystalli-                                                                            Heat                                                              Amount                                                                               zation generat-                                                                             Tensile                                                     (wt   tempera-                                                                              ion   strength                                             Compound                                                                              part) ture (°C.)                                                                     (cal/g)                                                                              (kg/cm.sup.2)                                __________________________________________________________________________     Comp. Ex. 53                                                                           --     --    295    0.7   940                                          Example 97                                                                             Compound-I                                                                            0.5   297    6.4   940                                          Example 98                                                                             "      1     298    7.3   940                                          Example 99                                                                             "      5     301    9.2   920                                          Example 100                                                                            "      15    305    9.3   840                                          Comp. Ex. 54                                                                           "      30    310    9.3   630                                          Example 101                                                                            Oligomer-I                                                                            0.5   296    2.1   940                                          Example 102                                                                            "      1     297    2.6   940                                          Example 103                                                                            "      5     298    8.0   920                                          Example 104                                                                            "      15    300    9.1   810                                          Comp. Ex. 55                                                                           "      30    304    9.3   620                                          Example 105                                                                            Oligomer-II                                                                           0.5   296    1.2   940                                          Example 106                                                                            "      1     298    1.7   940                                          Example 107                                                                            "      5     299    4.8   910                                          Example 108                                                                            "      15    302    7.2   810                                          Comp. Ex. 56                                                                           "      30    307    8.4   640                                          __________________________________________________________________________

                  TABLE 20                                                         ______________________________________                                                 Liquid crystal                                                                               Crystallization                                                  polymer       accelerater                                                                  Amount            Amount                                             Compound  (wt part) Compound                                                                               (wt part)                                ______________________________________                                         Example 109                                                                              Xydar      2        CaCl.sub.2                                                                             5                                        Example 110                                                                              "          5        "       5                                        Example 111                                                                              "         15        "       5                                        Example 112                                                                              "         30        "       5                                        Example 113                                                                              "         45        "       5                                        Comp. Ex. 57                                                                             "         60        "       5                                        Example 114                                                                              ECONOL     5        "       5                                        Example 115                                                                              "         30        "       5                                        Comp. Ex. 58                                                                             "         60        "       5                                        Example 116                                                                              Vectra     5        "       5                                        Example 117                                                                              "         30        "       5                                        Comp. Ex. 59                                                                             "         60        "       5                                        ______________________________________                                                  Spiral                                                                         flow      Tensile strength                                                       length      Unwelded  Welded                                                   (mm)        (kg/cm.sup.2)                                                                            (kg/cm.sup.2)                                 ______________________________________                                         Example 109                                                                               65          930       910                                           Example 110                                                                               80          930       890                                           Example 111                                                                               95          940       870                                           Example 112                                                                               120         950       790                                           Example 113                                                                               155         970       710                                           Comp. Ex. 57                                                                              180         950       570                                           Example 114                                                                               85          920       860                                           Example 115                                                                               130         930       710                                           Comp. Ex. 58                                                                              200         940       500                                           Example 116                                                                               75          910       890                                           Example 117                                                                               140         900       700                                           Comp. Ex. 59                                                                              220         900       550                                           ______________________________________                                          Note                                                                           CaCl.sub.2 : Kanto Kagaku Co.                                            

                  TABLE 21                                                         ______________________________________                                                 Liquid crystal                                                                              Crystallization                                                   polymer      accelerater                                                                   Amount            Amount                                             Compound  (wt part)                                                                               Compound (wt part)                                ______________________________________                                         Comp. Ex. 60                                                                             Xydar     30       --       --                                       Example 118                                                                              "         "        CaCl.sub.2                                                                              0.5                                      Example 119                                                                              "         "        "        1                                        Example 120                                                                              "         "        "        5                                        Example 121                                                                              "         "        "        15                                       Comp. Ex. 61                                                                             "         "        "        30                                       Example 122                                                                              "         "        AlPO.sub.4                                                                              0.5                                      Example 123                                                                              "         "        "        1                                        Example 124                                                                              "         "        "        5                                        Example 125                                                                              "         "        "        15                                       Comp. Ex. 62                                                                             "         "        "        30                                       Example 126                                                                              "         "        hydrotalcite                                                                            0.5                                      Example 127                                                                              "         "        "        1                                        Example 128                                                                              "         "        "        5                                        Example 129                                                                              "         "        "        15                                       Comp. Ex. 63                                                                             "         "        "        30                                       Example 130                                                                              "         "        NaCl     0.5                                      Example 131                                                                              "         "        "        1                                        Example 132                                                                              "         "        "        5                                        Example 133                                                                              "         "        "        15                                       Comp. Ex. 64                                                                             "         "        "        30                                       Example 134                                                                              "         "        graphite 0.5                                      Example 135                                                                              "         "        "        1                                        Example 136                                                                              "         "        "        5                                        Example 137                                                                              "         "        "        15                                       Comp. Ex. 65                                                                             "         "        "        30                                       ______________________________________                                                    D S C                                                                          Crystalli-  Heat                                                               zation      generat- Tensile                                                   tempera-    ion      strength                                                  ture (°C.)                                                                          (cal/g)  (kg/cm.sup.2)                                  ______________________________________                                         Comp. Ex. 60                                                                              315         1.1      960                                            Example 118                                                                               316         2.9      960                                            Example 119                                                                               318         4.5      960                                            Example 120                                                                               318         4.4      950                                            Example 121                                                                               320         4.9      860                                            Comp. Ex. 61                                                                              322         5.3      640                                            Example 122                                                                               315         2.0      960                                            Example 123                                                                               316         2.3      960                                            Example 124                                                                               317         2.8      940                                            Example 125                                                                               318         3.2      790                                            Comp. Ex. 62                                                                              318         3.1      620                                            Example 126                                                                               318         3.6      960                                            Example 127                                                                               320         4.6      960                                            Example 128                                                                               327         5.0      910                                            Example 129                                                                               330         5.3      820                                            Comp. Ex. 63                                                                              335         5.3      620                                            Example 130                                                                               311         2.6      960                                            Example 131                                                                               321         3.6      960                                            Example 132                                                                               323         3.7      960                                            Example 133                                                                               325         4.0      810                                            Comp. Ex. 64                                                                              325         4.1      560                                            Example 134                                                                               315         1.8      960                                            Example 135                                                                               317         4.1      960                                            Example 136                                                                               319         2.6      940                                            Example 137                                                                               322         2.9      890                                            Comp. Ex. 65                                                                              324         3.2      730                                            ______________________________________                                          Note                                                                           CaCl.sub.2 : Kanto Kagaku Co.                                                  AlPO.sub.4 : Junsei Kagaku Co.                                                 hydrotalcite: DHT4A2, Kyowa Kagaku Kogyo Co.                                   NaCl: Junsei Kagaku Co.                                                        graphite: Lonza Japan Co.                                                

                  TABLE 22                                                         ______________________________________                                                 Liquid crystal                                                                              Crystallization                                                   polymer      accelerater                                                                   Amount            Amount                                             Compound  (wt part)                                                                               Compound (wt part)                                ______________________________________                                         Example 138                                                                              Xydar      2       Compound-I                                                                              5                                        Example 139                                                                              "          5       "        "                                        Example 140                                                                              "         15       "        "                                        Example 141                                                                              "         30       "        "                                        Example 142                                                                              "         45       "        "                                        Comp. Ex. 66                                                                             "         60       "        "                                        Example 143                                                                              ECONOL     5       "        "                                        Example 144                                                                              "         30       "        "                                        Comp. Ex. 67                                                                             "         60       "        "                                        Example 145                                                                              Vectra     5       "        "                                        Example 146                                                                              "         30       "        "                                        Comp. Ex. 68                                                                             "         60       "        "                                        ______________________________________                                                    Spiral                                                                         flow       Tensile strength                                                    length     Unwelded  Welded                                                    (mm)       (kg/cm.sup.2)                                                                            (kg/cm.sup.2)                                  ______________________________________                                         Example 109                                                                                85        920       900                                            Example 110                                                                               100        920       870                                            Example 111                                                                               115        930       840                                            Example 112                                                                               140        940       750                                            Example 113                                                                               175        950       700                                            Comp. Ex. 57                                                                              200        940       520                                            Example 114                                                                               100        910       840                                            Example 115                                                                               150        920       690                                            Comp. Ex. 58                                                                              220        930       500                                            Example 116                                                                                90        900       870                                            Example 117                                                                               160        890       690                                            Comp. Ex. 59                                                                              240        890       520                                            ______________________________________                                    

                  TABLE 23                                                         ______________________________________                                                 Liquid crystal                                                                              Crystallization                                                   polymer      accelerater                                                                   Amount            Amount                                             Compound  (wt part)                                                                               Compound (wt part)                                ______________________________________                                         Comp. Ex. 69                                                                             Xydar     30       --       --                                       Example 147                                                                              "         30       Compound-I                                                                              0.5                                      Example 148                                                                              "         30       "        1                                        Example 149                                                                              "         30       "        5                                        Example 150                                                                              "         30       "        15                                       Comp. Ex. 70                                                                             "         30       "        30                                       Example 151                                                                              "         30       Oligoner-I                                                                              0.5                                      Example 152                                                                              "         30       "        1                                        Example 153                                                                              "         30       "        5                                        Example 154                                                                              "         30       "        15                                       Comp. Ex. 71                                                                             "         30       "        30                                       Example 155                                                                              "         30       Oligomer-II                                                                             0.5                                      Example 156                                                                              "         30       "        1                                        Example 157                                                                              "         30       "        5                                        Example 158                                                                              "         30       "        15                                       Comp. Ex. 72                                                                             "         30       "        30                                       ______________________________________                                                   D S C                                                                           Crystallization                                                                              Heat ge- Tensile                                                 temperature   neration strength                                                (°C.)  (cal/g)  (kg/cm.sup.2)                                ______________________________________                                         Comp. Ex. 69                                                                              315           1.1      950                                          Example 147                                                                               317           6.8      950                                          Example 148                                                                               318           7.7      950                                          Example 149                                                                               321           9.6      940                                          Example 150                                                                               325           9.7      840                                          Comp. Ex. 70                                                                              330           9.7      620                                          Example 151                                                                               316           2.6      950                                          Example 152                                                                               317           3.1      940                                          Example 153                                                                               318           8.5      920                                          Example 154                                                                               320           9.4      800                                          Comp. Ex. 71                                                                              324           9.6      620                                          Example 155                                                                               316           1.7      950                                          Example 156                                                                               318           2.1      940                                          Example 157                                                                               319           5.0      920                                          Example 158                                                                               322           7.7      820                                          Comp. Ex. 72                                                                              327           8.9      640                                          ______________________________________                                     

What is claimed is:
 1. A polyimide-based resin composition for sliding materials comprising from 1 to 60 parts by weight of fluororesin and from 5 to 160 parts by weight of carbon fiber for 100 parts by weight of a resin composition comprising from 50 to 99% by weight of a polyimide resin having recurring units represented by the formula (I): ##STR41## wherein X is a radical selected from the group consisting of a direct bond, sulfur, divalent hydrocarbon having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio, sulfonyl and ether; Y₁, Y₂, Y₃ and Y₄ are individually a radical selected from the group consisting of hydrogen, lower alkyl, lower alkoxy, chlorine and bromine; and R is a tetravalent radical selected from the group consisting of an aliphatic radical having from 4 to 9 carbon atoms, monocyclicaliphatic radical having from 4 to 10 carbon atoms, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or bridge member, and from 50 to 1% by weight of one or more thermotropic liquid crystal polymer.
 2. A polyimide-based resin composition for sliding materials of claim 1 wherein the thermotropic liquid crystal polymer is one or more polymer consisting of a fundamental structure having recurring units selected from the group consisting of the formulas (V), (VI), (VII) and/or (VIII): ##STR42##
 3. A polyimide based resin composition for sliding materials of claim 1 wherein the fluororesin is one ore more resin selected from the group consisting of the following (a) to (f):(a) tetrafluoroethylene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--

(b) tetrafluoroethylene-hexafluoropropylene copolymer resin having in the molecule recurring structural units represented by the formulas:

    --(CF.sub.2 CF.sub.2)--

    and

    --[CF(CF.sub.3)CF.sub.2 ]--

(c) tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin having in the molecule recurring structural units represented by the formulas:

    --(CF.sub.2 CF.sub.2)--

    and

    --[CF(OC.sub.m F.sub.2m+1)CF.sub.2 ]--

wherein m is an integer , (d) tetrafluoroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CF.sub.2)--

    and

    --(CH.sub.2 CH.sub.2)--

(e) trifluorochloroethylene-ethylene copolymer resin having in the molecule recurring structural units represented by the formula:

    --(CH.sub.2 CH.sub.2)--

    and

    --(CFClCF.sub.2)--

(f) fluorovinylidene resin having in the molecule recurring structural units represented by the formula:

    --(CF.sub.2 CH.sub.2)--. 